While "be nice" may sound like a platitude, the Hewlett-Packard CEO said it's some of the most important advice she ever got.

"I'll never forget my father telling me that," Whitman recalled in Fortune. "I had been mean to someone. He said, 'There is no point in being mean to anyone at any time. You never know who you're going to meet later in life. And by the way, you don't change anything by being mean. Usually you don't get anywhere.'"

The chairman of BP Capital Management was a student at Oklahoma State when his dad arrived on campus for his fraternity initiation — and delivered a life-changing message.

"A fool with a plan can outsmart a genius with no plan any day," he told Pickens. "And your mother and I think we have a fool with no plan. We think you’re wasting your time here in Stillwater. You’re not getting anywhere."

His dad was right, Pickens wrote on LinkedIn. "I had to admit I wasn’t burning up the place." But within a month of that visit, everything changed. He picked a track and switched his major. "I got a plan," he says, "and I've had one ever since."

These days, the former Microsoft CEO and his lawyer father give each other advice as co-chairs of the Bill and Melinda Gates Foundation, but back in the day, the elder Gates was the one doling out counsel to his son.

The most important lesson Gates ever learned from his dad? Invest in things — even if you're not good at them. In a conversation with Fortune, he recalled that both his parents encouraged him to "to go out for a lot of different sports like swimming, football, soccer," he says. "At the time I thought it was kind of pointless, but it ended up really exposing me to leadership opportunities and showing me that I wasn't good at a lot of things, instead of sticking to things that I was comfortable with."

His father agrees that those early forced softball team memberships seem to have worked out okay. "Apparently it turned out to be good advice."

"When I grew up our house was always a hive of activity, with Mum dreaming up new entrepreneurial schemes left, right and centre, and me and my sisters running wild," the Virgin Group founder wrote in a LinkedIn post.

Amidst the chaos, Branson's dad was an anchor of calm and support. "He wasn’t quiet, but he was not often as talkative as the rest of us. It made for a wonderful balance, and we always knew we could rely on him no matter what."

"Within this discreet support lay one of his best and most simple pieces of advice for me: listen more than you talk," he says. "Nobody learned anything by hearing themselves speak."

If Apple is defined in part by their commitment to beautiful design, then Paul Jobs — Steve Jobs' adoptive father — may be the person to thank.

"Paul Jobs was a salt-of-the-earth guy who was a great mechanic. And he taught his son Steve how to make great things," Jobs' biographer, Walter Isaacson, told CBS News.

"Once they were building a fence. And he said, 'You got to make the back of the fence that nobody will see just as good looking as the front of the fence. Even though nobody will see it, you will know, and that will show that you're dedicated to making something perfect.'"

The lifestyle mogul said she never would have been able to take the risks that have lead to her success without a key piece of advice from her dad.

"He told me that with my personal characteristics, I could, if I set my mind to it, do anything I chose," she wrote in a post on LinkedIn. "This advice instilled in me a great sense of confidence, and despite the fact that sometimes I was a little nervous, I stepped out and did what I wanted to do when I wanted to do it."

Growing up in Paris, El-Erian — now the chief economic advisor at Allianz — learned the value of getting out of his comfort zone from his dad, then Egypt's ambassador to France.

"Each day we used to get at least four daily newspapers, from Le Figaro on the right side of the political spectrum to L'Humanité, which was the newspaper of the Communist Party," he told Fortune.

"I remember asking my father, Why do we need four newspapers? He said to me, 'Unless you read different points of view, your mind will eventually close, and you'll become a prisoner to a certain point of view that you'll never question.'"

The president and CEO of Charles Schwab told Fortune that the paternal advice that's shaped his life the most is also some of the simplest. "Most things in the world can be bought or sold," his father said to him, "but not a reputation."

"With these few words of great wisdom, my father instilled in me a framework for behavior, interactions with others, and decision making that shapes my actions every day," he explained.

Real estate superstar Corcoran caught the entrepreneurial bug from her dad.

"[My father] would quit his job when the boss told him to do something," she explained in Inc. "It was an M.O. If he came home before 5:30 we knew he had been fired. And we all sat at the table early for dinner promptly at 6, because my mother was like a lieutenant. And he would say, 'Guess what, kids?' And we'd all shout together, 'You were fired?!' And that was the most exciting meal of the month."

That spirit was contagious, she says, and it's the reason she is where she is today. "My father taught us a great heaping of insubordination and I think that's why [his children] didn't want to grow up working for anybody."

The PepsiCo president and CEO got a piece of advice from her dad that changed the way she approached the world. "Whatever anybody says or does," he told her, "assume positive intent."

It's a simple shift, but the results can be huge, she explained to Fortune. "You will be amazed at how your whole approach to a person or problem becomes very different. When you assume negative intent, you're angry. If you take away that anger and assume positive intent, you will be amazed."

Instead of getting defensive, you'll be able to really listen to other people — and moreover, other people will be able to really listen to you. "[W]hen you assume positive intent, I think often what happens is the other person says, 'Hey, wait a minute, maybe I'm wrong in reacting the way I do because this person is really making an effort.'"

The billionaire tech entrepreneur, investor, and Dallas Mavericks owner knows there's more to life that business, and he learned it from his dad.

"My dad is 87. He’s going strong, he's a machine," he told the crowd at South by Southwest in 2014. "My dad says it over and over, 'Today’s the youngest you’re ever going to be. You’ve got to live like it. You've got to live young every day.' And that’s what I try to do."

Spanx might not be a billion dollar company today were it not for Blakely's father's dinnertime routine.

"My dad used to ask my brother and me at the dinner table what we had failed at that week," she told the audience at a 2015 Network for Teaching Entrepreneurship event in New York City. "I can remember coming home from school and saying, 'Dad, I tried out for this and I was horrible!' and he would high-five me and say, 'Way to go!' If I didn't have something that I had failed at, he actually would be disappointed."

There's a lot in this world that's out of our control. But if the American Express CEO learned one lesson from his dad, it's to focus your energy on the things you can.

"If you're going to focus on anything, focus on what you can control," he said, addressing the audience at the McComb School of Business at the University of Texas-Austin. "And the only thing you can control is your performance."

It's empowering advice, he pointed out. "[W]hat it says to a person is you can really make a difference. You can really make a difference off your performance."

The former Microsoft CEO and current owner of the Los Angeles Clippers said the best piece of advice he ever got — "bar none" — came from his father.

"My dad said, 'If you're going do a job, do a job. And if you're not going to do a job, don't do a job. And that is the key of everything," he explained in an interview at Oxford's business school.

In other words: go all in. "If you're going to do something, then do it heart, body, and soul," he said.

24 of the best pieces of advice ever given to graduates