When you're hovering by your gate at one of the most frustrating airports in the US, holiday travel can seem more tedious than fun.

For that reason, it's imperative that you do everything you can to make it go smoothly — like, for instance, packing the perfect carry-on.

Even if your luggage isn't lost (fingers crossed), you'll no doubt be glad to have a fully-stocked bag on hand at all times. 

At the very least, it will spare you the expense of having to buy temporary replacements while your sweater/snacks/toothbrush idle in the bowels of an airplane.

As far as what should go in said bag, we asked experts and scoured the web to figure out what you'll need by your side.

This post was originally written by Mandi Woodruff.

Stop paying for airport WiFi and stay connected with your own MiFi hotspot.

Unless you're interested in shelling out up to $12 to use airport WiFi, it's a good idea to invest in a WiFi hotspot of your own. 

With its slim, credit card-sized package and simple access to 4G networks, personal MiFi hotspots like the Verizon Jetpack 4G LTE MiFi are a personal favorite of Yahoo! CEO Marissa Meyer and David Rush, cofounder and CEO of Earshot.

"It is a huge time-saver because you always know you can stay connected regardless of your location," Rush told Business Insider. 

Bring a reusable water bottle to fill after going through security.

"My number one tip is to invest in a water bottle with a filter," said Talia Salem, a communications rep for PlanetWildlife. "I have taken this all over the world and it has saved me hundreds of dollars."

Brand is up to you (there are dozens to choose from online). Salem is a fan of the Camelback Groove ($25) and we're crazy for AquaGear water filtration bottles ($29.99). 

They remove 99.99% of tap water contaminants and can save up to 600 plastic bottles over their lifetime.

Pack a small kit with medicines, band aids, and first aid essentials.

If you've ever paid $10 for a minuscule bottle of aspirin at an airport kiosk, you'll appreciate this tip.

Stock up on essentials like pain reliever, band aids, vitamins and cough drops before heading out on your flight, and be sure to pack them in your carry-on.

A fortune has to start somewhere.

For Mavericks owner Mark Cuban it was selling garbage bags. For Berkshire Hathaway CEO Warren Buffett it was knocking on doors and selling packs of gum. For "Shark Tank" icon Daymond John it was a matter of re-purposing pencils for girls he had a crush on.

Looking into how these legends got started reveals a lot about the personalities of the people who create extreme wealth.

Let's get to the stories.

Daymond John wooed girls in his first grade class by customizing pencils for them.

"I never knew anything other than wanting to be an entrepreneur,"John tells Business Insider. Before he made a fortune from launching the clothing line FUBU in the '90s, John learned the power of sales in first grade.

In a recent speech at Rutgers, John explained that he would scrape the paint off pencils and paint his customer's name on them for a fee — and his market was exclusively the prettiest girls in class.

Sales were good until the principal shut down the operation after discovering John was stealing all of the pencils from boys he didn't like.

Ikea founder Ingvar Kamprad rode around his tiny Swedish town selling matches.

The man who built Ikea has been looking for a better way to sell since the 1930s.

Now 88, a 5-year-old Ingvar Kamprad was growing up on a farm in rural Sweden when he showed the first signs of the entrepreneurial itch. The kid rode to his neighbors' houses selling matches.

He started earning his reputation for finding efficiencies way back then: He would buy matches in bulk from Stockholm then sell them individually at a markup — but still at a reasonable price.

That business grew into other home supplies, which then turned into furniture. At age 17, he started Ikea.

Mark Cuban learned the basics of business as a 12-year-old selling trash bags.

The billionaire owner of the Dallas Mavericks and star "Shark Tank" investor started his career as an entrepreneur out of necessity.

When he was 12, he approached his dad one night to ask him for a pair of expensive sneakers. His dad was playing poker and drinking with some friends, which happened to work out in Cuban's favor.

"And one of his buddies popped up ... He said, 'I got somethin' for ya! I've got these garbage bags I need to sell. Why don't you go out there and sell these garbage bags?'" Cuban tells Bloomberg's Barry Ritholtz in a Masters in Business podcast.

The bags were sold in boxes of 100 for $6. Cuban went door to door in his neighborhood and convinced customers that since they'd be buying trash bags anyways, they might as well buy them at a cheaper price from him.

On Tuesday, HBO revealed it has 160 lawyers preparing for its new documentary on the Church of Scientology.

The documentary is based on Pulitzer Prize-winning author Lawrence Wright's controversial book "Going Clear: Scientology, Hollywood, & the Prison of Belief," which grew out of a New Yorker profile on former Scientologist director Paul Haggis.

See Scientology's most famous followers >

The new HBO documentary "is expected to feature new revelations about the controversial religion and its famous followers Tom Cruise and John Travolta," according to The Hollywood Reporter.

Cruise, Scientology's most prominent member, became involved with the church in 1990 through his first wife, actress Mimi Rogers.

"It's a privilege to call yourself a Scientologist, and it's something that you have to earn,"Cruise said in 2004.

In 2005, he told Matt Lauer on "Today," "It is a religion. Because it's dealing with the spirit — you as a spiritual being. It gives you tools you can use to apply to your life."

By 2013, Cruise admitted that ex-wife Katie Holmes divorced him in part to protect the couple's daughter Suri from Scientology. He also admitted that Suri is no longer a practicing member of the church.

Cruise, however, is still an active member — and he's not the only one. From "Mad Men" to "The Simpsons," see who practices Scientology. 

Actress Kirstie Alley

The former "Cheers" star says the religion helped her overcome a cocaine addiction. 

In 2010, rumors swirled her weight loss program, Organic Liaison, was a front for Scientology, a claim the actress vehemently denied. 

Actress Bijou Phillips

Indie goddess Bijou Phillips, most recently known for her role on "Raising Hope," is daughter of the "Mamas and Papas" singer John Phillips.

Bijou is married to Danny Masterson and the two frequently go to Scientology events together. 

Actor Danny Masterson

Masterson is best-known for his role on "That '70's Show." He defended Tom Cruise for the actor's leaked Scientology video back in 2008. 

In an interview with Paper Magazine in 2009 he explained the religion as follows:

"The definition of Scientology is 'the study of knowledge,'"said Masterson. "Obviously, the more knowledge you have in a given field, such as life, the more confident you are as a person."

If you decided to stay in and avoid the crazy crowds on Black Friday, the good news is there are plenty of deals to choose from on Cyber Monday, too.

A bunch of retailers including Wal-Mart and Amazon will be offering discounts that you can take advantage of without having to leave your home.

Most stores like Best Buy and Target aren't announcing deals until Dec. 1, but we've rounded up the best discounts we've come across so far.

From giant HD TVs to gaming console bundles, here are some of the best Cyber Monday deals in tech.

Motorola's Moto X will be super cheap on Monday.

Motorola announced that the Moto X, which we've called one of the best Android phones of the year, will be on sale for just $0.01 when you sign up for a two year contract with Verizon. If you opt for the contract-free unlocked version, you'll get a $140 discount which brings the price down to $359 from $500. 

Wal-Mart is offering an excellent deal on the PlayStation 4.

If you've been eyeballing a PlayStation 4, you should seriously consider buying one on Cyber Monday. Wal-Mart is offering a super cheap bundle deal that includes the console itself, "Lego Batman 3,""Little Big Planet 3," a game of your choice, and an extra controller for just $450. That's an incredible deal, considering the console on its own usually costs $400. 

You can also get a 4K TV for $500 cheaper at Wal-Mart.

Wal-Mart is also selling a 55-inch 4K Ultra HD TV made by Samsung for $998, which is a $500 drop from its normal price.

Nobody expects the food on airplanes to be good. But some do it better than others. 

The "World Airline Awards"compiles an annual ranking of the best meals you can get when flying in business class. We got photos of those dishes from AirlineMeals.net, an online database of thousands of photos and food reviews from airlines around the world.

Lick your lips!

10. South Africa Airways. When flying out of Johannesburg you could try this sophisticated crayfish and chicken timbale.

9. Emirates. This chocolate ganache cake, served on a flight from Dubai to Dallas, looks super yummy.

8. All Nippon Airways. If you fly to Japan, expect some sushi to be served.

Pinterest's grand vision is to fill the gap between an idea and a specific search, and to help people find things they didn't know they were looking for.   

There are 30 billion Pins in the social network's system and that number grows by 25% every quarter. 

Although some people still assume the site's just for cupcakes and wedding inspiration, there are a bunch of ways that people are using Pinterest that you may never have thought of. 

Because it's possible to play videos directly from Pinterest, you can create playlists.

A bunch of Pinterest users post workout inspiration, which means you can build a fitness plan through the site.

When you pin recipes, Pinterest will often list the ingredients, making an automatic grocery list if you find something you can't wait to make!

For many students, a college degree puts you on the direct path to a certain career, such as a doctor, teacher, or journalist. 

But for many others, the future isn't as clear cut.

Maybe you want to go to med school, but don't necessarily want to be a doctor. Maybe you love maps, but aren't sure how to incorporate that passion into a career. Or perhaps you just haven't found anything that sounds appealing yet. 

Luckily, there are tons of great career options out there that many college kids have no idea even exist. In this helpful thread, Reddit users shared some of these under-the-radar occupations that most students probably haven't heard of. A fun bonus: most of them are pretty lucrative as well. 

Here are 16 of our favorites, including salary data from the US Bureau of Labor Statistics, for those who need some inspiration finding their dream job.

Did we forget any awesome, lesser-known jobs? Let us know in the comments.

Air traffic controller

Median annual salary: $122,530

"After school and training it pays an average of 100k a year, but there is an age limit to get accepted."—Kate1320

"My father is an ATC at Pearson. 200k a year with brilliant benefits. He provided a great quality of life for my family."—1stOnRT1

Court stenographer

"It's a three-year program (on average — took me four to finish), but if you're proficient in grammar, have strong language skills, have solid finger dexterity from playing an instrument or video games, and are able to work independently, it's an incredible career.

"You work from home most of the time, lawyers very rarely schedule depositions before 10:00 am, you can make your own schedule, and the pay is great. Your pay reflects how hard you want to work and the jobs you're getting, but I made 65k my first year and nearly 80k my second."—Bad_Karma21

Industrial design

Median annual salary: $59,610

It's flu season, and you're starting to feel under the weather — hopefully it's just a cold.

Even though hunger may not be on your mind, you're convinced that a cup of chicken noodle soup is exactly what you need.

But will it make you feel better? There's an old saying about this, but how does it go again, is it starve a fever and feed a cold, or the other way around?

There are plenty of folk sayings and "tips" about everything from staying healthy to avoiding a hangover. 

The only problem is that a lot of folk wisdom about health and nutrition is totally — or at least mostly — wrong.

Here's the truth behind some of those health claims you've heard all your life, but might not hold water at all.

Bundle up or you’ll catch a cold.

Sorry mom, but being physically cold isn't what gets you sick. There's no evidence that going outside with wet hair when it's freezing will make you sick — provided you avoid hypothermia.

But there is a scientifically sound explanation for why people catch more colds in winter. Because we spend more time in close quarters indoors, it is more likely that we'll cross paths with a cold-causing virus spread from another person during the winter. 

The chemical tryptophan in turkey makes you sleepy.

Who doesn't love the post-Thanksgiving nap? Turkey contains tryptophan after all, an amino acid that is a component of some of the brain chemicals that help you relax.

But plenty of foods contain tryptophan. Cheddar cheese has even more than turkey — and cheddar is never pointed out as a sleep inducing food. Experts say that instead, the carbs, alcohol, and general size of the Turkey-day feast are the cause of those delicious holiday siestas. 

Taking your vitamins will keep you healthy.

Vitamins sound like a great idea. One pill that can provide you everything you need to be healthy!

If only they worked. Decades of research on vitamins reviews don't find any justification for our multivitamin habit, and in some cases, vitamins have actually been associated with an increased risk of various cancers.

"If it has to happen, then it has to happen first," writes Laura Vanderkam, time management expert and author of "What the Most Successful People Do Before Breakfast."

Those among us who have managed to find professional success and eke out a life actively embrace this philosophy. They must set aside their first hours of the day to invest in their top-priority activities before other people's priorities come rushing in.

Science supports this strategy. Vanderkam cites Florida State University psychology professor Roy Baumeister's famous finding that willpower is like a muscle that becomes fatigued from overuse. Diets, he says, come undone in the evening, just as poor self-control and lapses in decision-making often come later in the day. On the other hand, early mornings offer a fresh supply of willpower, and people tend to be more optimistic and ready to tackle challenging tasks.

So what do successful executives and entrepreneurs do when they are rested and fresh? From Vanderkam's study of morning rituals, we outline the following 12 things that the most successful people do before breakfast.

They wake up early.

Successful people know that time is a precious commodity. And while theirs is easily eaten up by phone calls, meetings, and sudden crises once they’ve gotten to the office, the morning hours are under their control. That’s why many of them rise before the sun, squeezing out as much time as they can to do with as they please.

In a poll of 20 executives cited by Vanderkam, 90% said they wake up before 6 a.m. on weekdays. PepsiCo CEO Indra Nooyi, for example, wakes at 4 a.m. and is in the office no later than 7 a.m. Meanwhile, Disney CEO Bob Iger gets up at 4:30 to read, and Square CEO Jack Dorsey is up at 5:30 to jog. 

The bottom line: Productive mornings start with early wake-up calls.

They exercise before it falls off the to-do list.

The top morning activity of the rich and powerful seems to be exercise, be it lifting weights at home or going to the gym. According to Vanderkam, Xerox CEO Ursula Burns schedules an hour-long personal training session starting at 6 a.m. twice a week; Christie's CEO Steve Murphy uses the mornings to do yoga; and Starwood Hotels CEO Frits van Paasschen runs for an hour every morning starting at 5:30.

“These are incredibly busy people,” says Vanderkam. “If they make time to exercise, it must be important.”

Beyond the fact that exercising in the morning means they can’t later run out of time, Vanderkam says a pre-breakfast workout helps reduce stress later in the day, counteracts the effects of high-fat diet, and improves sleep.

They work on a top-priority business project.

The quiet hours of the morning can be the ideal time to focus on an important work project without being interrupted. What’s more, spending time on it at the beginning of the day ensures that it gets your attention before others (kids, employees, bosses) use it all up.

Vanderkam uses the example of business strategist Debbie Moysychyn, who dealt with so many ad hoc meetings and interruptions throughout the day that she felt she couldn’t get anything done. She started thinking of the early mornings as project time, and chose a top-priority project each day to focus on. Sure enough, not a single colleague dropped in on her at 6:30 a.m. She could finally concentrate.

We all want the same thing from our gifts: to make someone else happy.

Sometimes, though, it's a tricky balance between making our families and friends happy and maxing out the credit card.

Never fear.

We found 50 gifts that are bound to please anyone on your list — and you never have to show them the price tag.

In fact, you'd be amazed at what $50 can buy.

Click here for the full list »

Or find the right section for you: 

For everyone on your list »

For the traveler »

For the gym rat »

For the host »

For the Instagrammer »

For the office gift exchange (under $10) »

Gifts that give back »

FOR EVERYONE ON YOUR LIST

Stream TV straight from your phone with Chromecast.

Cable TV is quickly becoming a thing of the past, but there's still something to be said for watching your favorite shows on a bigger screen than your phone or laptop.

Google's Chromecast plugs straight into your TV and allows you to stream sites including Netflix, HBO Go, and YouTube right from your computer or phone to the big screen.

Plus, until the end of 2014, a new Chromecast comes with two free months' subscription to Hulu Plus.

Price: $35

Do something different after dinner with Bananagrams.

Anyone from your first-grade niece to your 80-year-old grandfather can join in on Bananagrams, the Scrabble-esque word game.

It comes in a silly, easily portable pouch and doesn't require a board, so you can simply push plates aside at the dinner table and start playing. 

Price: $10.24

CEOs are known for pulling in a pretty penny. But doctors make even more.

That's right: On average, those sporting scrubs and stethoscopes bring home fatter paychecks than those donning suits and ties, according to the latest Bureau of Labor Statistics' Occupational Employment and Wage Estimates survey.

The survey, which reflects May 2013 salary and employment data gathered from more than one million businesses, found that 15 of the nation's top 25 highest-paying occupations are in the medical field.

The best-paying job of all: anesthesiologist. 

On average, anesthesiologists in the US earn $113 an hour, for a mean annual salary of $235,070.

According to the American Society of Anesthesiologists (ASA), these medical doctors are responsible for the safety and wellbeing of patients before, during, and after surgery. In the US, they're required to complete a four-year undergraduate college degree, four years of medical school, and a four-year anesthesiology residency program. Most anesthesiologists become board certified, and many complete an additional fellowship year of specialty training.

A 2014 physician compensation report by Medscape found that nearly 80% of anesthesiologists spend 40 hours or more per week with patients.

25. Sales Managers

Mean annual pay: $123,150

Number of people who hold this job in the US: 352,220

Projected growth (2012 - 2020): 8%

24. Financial Managers

Mean annual pay: $126,660

Number of people who hold this job in the US: 499,320

Projected growth (2012 - 2020): 9%

23. Prosthodontists

Mean annual pay: $128,310

Number of people who hold this job in the US: 290

Projected growth (2012 - 2020): 16%

According to the BLS these professionals construct oral prostheses to replace missing teeth to correct natural and acquired deformation of the mouth and jaws, to restore and maintain oral function, such as chewing and speaking, and to improve appearance.

Though many college students choose their major based on how much money they will be able to earn in the real world, it's important to consider whether your future job will be one you feel good about doing.

The salary information website PayScale.com decided to figure out which majors lead to the most emotionally fulfilling careers.

To do this, PayScale used data people submitted about their jobs, and ranked 207 college majors based on what percentage of degree-holders responded "yes" or "very much so" to the question, "Does your work make the world a better place?"

In several instances where two majors had the same percentage of "meaningful" responses, we gave deference to the major that had a higher starting salary.

Many of them are the "helping professions," as you'll see.

20. Foods & Nutrition

Grads who find their job meaningful: 71%

Average starting salary: $39,100

Average mid-career salary: $59,800

Potential careers: Clinical nutrition manager, supermarket department manager, operations manager for a fast-food chain.

Source: Payscale 2014-2015 College Salary Report

19. Nuclear Engineering

Grads who find their job meaningful: 71%

Average starting salary: $67,000

Average mid-career salary: $118,800

Potential careers: Nuclear engineer, director of engineering, engineering technician.

Source: Payscale 2014-2015 College Salary Report

18. Exercise Science

Grads who find their job meaningful: 72%

Average starting salary: $34,400

Average mid-career salary: $53,400

Potential careers: Computer science professor, biology professor, earth science professor. 

Source: Payscale 2014-2015 College Salary Report

Three years ago, Twitter announced that it was moving into a deserted building in one of the worst parts of San Francisco.

Twitter made the move because the city had created a new tax-free zone in that neighborhood, known as Mid-Market. 

We took a walk around the neighborhood in July 2011 to see exactly what Twitter was getting itself into. It didn't look pretty. But Twitter made the move, and a bunch of other tech companies followed. Then came the residential developers. Then the other businesses.

Three years later, the change is startling. See for yourself ...

First, a reminder. This is what the building looked like before Twitter moved in.

Here's what it looks like today.

The most obvious change is the number of people in the street. In this picture from three years ago, this neighborhood didn't have much foot traffic at all. It was kind of grim.

It's time to get serious about holiday shopping.

Trying to decide on the perfect laptop, tablet, or tech accessory can be overwhelming.

Manufacturers release tons of gadgets all year, so sifting through all of your options to find the best fit can be overwhelming.

Our holiday gift guide is full of excellent ideas — whether you're trying to find a new laptop for your son or daughter going away to college, some new cases and accessories to use as stocking stuffers, or the best entertainment devices to spice up your living room.

iPhone 6 and iPhone 6 Plus are the two best phones you can buy.

For most people, the iPhone 6 is the best smartphone. The iPhone 6 Plus, with a larger 5.5-inch screen, is the best phone if you want a phablet.

Why? Both phones are the perfect blend of design, app selection, ease of use, and powerful hardware.

Click here for the iPhone 6 and 6 Plus review >>

Price: Starts at $649 for the iPhone 6 and $749 for the iPhone 6 Plus. 

The HTC One M8 is the most beautiful Android phone.

HTC's flagship phone, the HTC One (M8), is the best Android phone you can buy.

Like the original, the new HTC One, which is also called the M8, has a gorgeous design and high-quality metal construction. It also has an extra rear camera that acts as a depth sensor so you can edit photos later and change the focus.  

Click here for the HTC One (M8) review>>

Price: Around $540

Americans sit through some 11 million meetings every day— with the unproductive ones costing companies $37 billion a year. 

We've already learned that meetings fall apart thanks to sloppy agendas, un-articulated ground rules, and other structural mistakes. 

So we decided to look at how some of the most effective executives in history — from GM czar Alfred Sloan to Apple prince Steve Jobs to Facebook queen Sheryl Sandberg — run the meetings that invariably fill their calendars. 

Here's what we found. 

Legendary GM CEO Alfred Sloan said little — then made follow-ups.

Alfred Sloan ran GM from the 1920s to the '50s. During that time he led GM to become the world's largest corporation— in the '50s, GM held 46% of the US auto market and employed over 600,000 Americans. 

Sloan is also credited with inventing modern corporate structure. 

According to leadership guru Peter Drucker, the follow-up memo was one of Sloan's go-to tools. 

After any formal meeting — in which he simply announced the purpose, listened to what people had to say, and then left — Sloan would send a follow-up memo with a plan of action. 

Drucker's take: 

[Sloan] immediately wrote a short memo addressed to one attendee of the meeting. In that note, he summarized the discussion and its conclusions and spelled out any work assignment decided upon in the meeting (including a decision to hold another meeting on the subject or to study an issue). He specified the deadline and the executive who was to be accountable for the assignment. He sent a copy of the memo to everyone who'd been present at the meeting.

These memos made Sloan an "outstandingly effective executive," Drucker argues, and you might say they were a key to GM's dominance of the 20th century. 

Opsware CEO and Andreessen Horowitz cofounder Ben Horowitz likes to have one-to-one meetings.

Back when he was a CEO, Ben Horowitz led Opsware to a $1.6 billion sale to HP in 2007.

Two years later, he cofounded Andreessen Horowitz, probably the most sought-after firm in venture capital. 

Horowitz, who spends much of his time mentoring young leaders, says that most important job for a CEO is to architect the way people communicate in a company. 

The one-to-one meeting is essential to that process, he says, as it's the best place for ideas and critiques to flow up from employees to management.

Here's his take on how to run one: 

If you like structured agendas, then the employee should set the agenda. A good practice is to have the employee send you the agenda in advance.

This will give her a chance to cancel the meeting if nothing is pressing. It also makes clear that it is her meeting and will take as much or as little time as she needs.

During the meeting, since it’s the employee’s meeting, the manager should do 10% of the talking and 90% of the listening. Note that this is the opposite of most one-on-ones. 

Tesla CEO Elon Musk demands that people be super prepared.

Musk has incredibly high standards. He has a reputation for firing people if they miss a deadline. So if you're meeting with him at Tesla or SpaceX, you have to be ready.

As one anonymous Musk employee shares on Quora:

When we met with Elon, we were prepared. Because if you weren't, he'd let you know it. If he asked a reasonable follow-up question and you weren't prepared with an answer, well, good luck.

What else would you expect from the most badass CEO in America? 

Click here to see our verdict >>

Join the conversation about this story »

A few years ago, not many people knew the name Benedict Cumberbatch.

Now, the 38-year-old actor has an Emmy-winning miniseries, "Sherlock," and a rabid fan following known as the "Cumberbitches." Dozensupondozens of Tumblr pages are devoted to the London-born actor.

In his latest role, he plays brilliant British cryptanalyst and war hero Alan Turing in "The Imitation Game," opening in theaters Nov. 28th. 

He also plays not one, but two villains in "The Hobbit: The Battle of the Five Armies."

Benedict Cumberbatch was born in London in the summer of '76 to actor parents Wanda Ventham and Timothy Carlton. He said he had a "great childhood," though he was "over-gregarious" and "prone to moments of hyperactivity, then exhaustion and bad temperedness."

Source: ElleUK

His parents tried to dissuade him from acting by sending him to Harrow, one of the oldest, most-respected all-male boarding schools in the United Kingdom. He describes the experience as "a bit embarrassing.""Luckily I was on the rugby team, so I was macho at the same time!"

Source: ElleUK, PBS

While he also painted at school, he couldn't escape the theater. One of his earliest roles was playing Titania, Queen of the Fairies in William Shakespeare's "A Midsummer Night's Dream."

Source: Digital Spy

For busy, successful people, sleep is a precious commodity — rare and treasured.

So when it comes to getting a solid night of shut-eye, some do everything they can to not let insomnia, pressure at work, or snoring spouses get in the way — even if that means creating a weird nightly routine or napping to get through the day.

Here's a look at the most bizarre sleeping habits of 13 highly successful people.

This is an updated article originally written by Vivian Giang.

Tom Cruise sleeps in a sound-proof 'snoratorium.'

Cruise's snores are apparently so bad, he sleeps in a sound-proof "snoratorium." Once a nursery, Cruise converted the small room at the back of his house to a sound-proof space where he can snore in peace.

"Whoever uses the snoring room cannot be heard outside the locked door," an alleged visitor to the actor's house told the Daily Mail. "It's very small, comfortable, and dark."

Winston Churchill took a two-hour nap every day.

Every day at 5 p.m., the prime minister would drink a weak whiskey and soda before taking a two-hour nap. Churchill said this short "siesta"allowed him to get one and a half day's worth of work out done every 24 hours.

Churchill would often work through the night and became known as quite the night owl. Due to his irregular sleep schedule, he was said to hold War Cabinet meetings in his bath.

Mariah Carey surrounds her bed with 20 humidifiers and needs 15 hours of shut-eye per night.

"I've got to sleep 15 hours to sing the way I want to,"Carey told Interview magazine in 2007.

The singer also admitted to sleeping with 20 humidifiers around her bed, which soothe sore throats and add moisture to dry air. "Basically, it's like sleeping in a steam room," she said.

Building a successful business from the ground up isn't easy, and no one does it alone.

For the entrepreneurs who make it, the difference between giving up and persisting through the toughest times can be getting advice from people who have done it before — and being smart enough to listen. 

From billionaire Mark Cuban's dad telling him that there are no shortcuts to Lululemon founder Chip Wilson's realization that people actually enjoy helping others, we asked 15 successful entrepreneurs to share the best advice they ever got, discovering the lessons that stick with them to this day. 

Max Nisen contributed to an earlier version of this article.

Billionaire Mark Cuban: There are no shortcuts.

The investor and owner of the Dallas Mavericks tells Business Insider the best advice he ever got was: "Do the work. Out-work. Out-think. Out-sell your expectations. There are no shortcuts." The advice came from his father, who did upholstery on cars, when Cuban was in high school. "He was always very encouraging but also realistic," Cuban says of his dad.

Restaurateur Jon Taffer: See every detail of your business.

"Years ago when I was very young," recalls Taffer, the host of TV show "Bar Rescue" and a former business owner, in a recent interview with Business Insider, "a VP of Hyatt looked at me and said, 'You look, but you don’t see.'" Taffer learned to look not just at the big picture, but also at every place setting, light fixture, and customer exchange. "See every crack, every detail. I learned to really see and not just look at my business," he says. 

FUBU founder Daymond John: Don't chase the money.

When he was growing up, John's mother said, "Money is a great slave but a horrible master." 

"In the earlier days, I was really doing things because I thought what I wanted was to be rich,"the "Shark Tank" investor tells Business Insider's Richard Feloni. "For the most part, those businesses failed, and then later when I started doing something casually because I loved it, that business burst."

"So all those old sayings that your grandmother and grandfather used to tell you are actually somewhat real," John continues. "I learned that over the years. And then after becoming wealthy and having money, I failed at a lot of things, and that reinforced some of those theories that I was told at a young age."

The worst part of going out to dinner with a group of friends is figuring out who owes what at the end of the night. All too often, once everyone's chipped in, there's either not enough money on the table, or way too much.

When trying to plan for retirement, or figure out whether to make an investment, one helpful thing to know is how long it will take to double your initial capital.

And when you're considering taking a new job with an annual salary, it might be useful to know how that salary compares with what you'd earn at a job with an hourly pay rate.

Some handy math tricks can help you figure out each of these situations quickly — and without having to resort to pulling out the calculator on your phone. We've assembled seven such tricks and talk a little about how they all work.

Eric Platt and Walt Hickey contributed to earlier versions of this article.

WATCH: We Did The Math: Which iPhone 6 Should You Buy?

Converting your salary to an hourly figure

The Trick: Take your salary, drop the last three zeros, and then divide by two.

Example: So if you earn $40,000, you're left with $20 an hour.

Maybe you're a salaried employee trying to figure out whether you should take that job that pays by the hour. This trick would certainly help.

This comes from making a couple of assumptions about your working hours and some quick observations about time. There are 52 weeks in a year, and so if you're working a 40 hour week for 50 of those weeks, you'll be working 40 x 50 = 2,000 hours in a year. Take your annual salary and divide by those 2,000 hours (equivalently, drop the last three zeros and divide by two), and voila, you get your hourly rate.

Figuring out sales tax and tips

The Trick: Assuming an approximately 9% sales tax, as in New York, if you take your pre-tax part of the bill, divide by four, and add this amount to the pre-tax part, you'll be leaving about a 16% tip. If you're feeling more generous, divide by three and add that amount instead, leaving about a 24% tip.

Example: Say your part of the pre-tax bill comes to $18. If you want to leave a 16% tip, divide $18 by four to get $4.50. Add that to your $18 pre-tax cost, and leave a total of $22.50. If you want to leave a larger tip, divide $18 by three to get $6, and combine that with the pre-tax cost to leave a total of $24.

Here's why this works: Dividing the pre-tax bill by four is the same as taking 25% of that amount. That's enough money to cover the 9% sales tax, with 16% leftover for the tip, because 25 - 9 = 16. Similarly, dividing by three gives about 33% of the pre-tax bill, covering the 9% sales tax and a 24% tip, because 33 - 9 = 24.

Business Insider's Sarah Schmalbruch also recently wrote about a few other nice tricks to calculate tips, like moving the decimal point one place to the left and multiplying by two to find 20% of the bill.

So, if the bill is $18, the moving the decimal points gets you $1.80. And multiplying it by two gets you $3.60.

How long it'll take to double your investment

The Rule of 72: Need an easy way to determine how long it will take to double your investment? Simply divide the number 72 by your projected growth rate.

Example: So, if you're getting a return of 9% per year, it will take about eight years for your investment to double in size, because 72/9 = 8.

The rule of 72 comes from manipulating the basic mathematical formula for calculating compound interest. The exact number you need to divide your growth rate by is actually closer to 69, but 70 or 72 are frequently used for quick mental estimates, because most common single-digit rates of return will divide evenly into one of these.