To kick off Global Entrepreneurship Week, I spent the morning at the New York Stock Exchange at an event called "Mentoring Madness," sponsored by NYSE Euronext and the Kauffman Foundation. A roomful of eager, aspiring college entrepreneurs soaked up advice from a panel of inspiring veterans, including Blake Mycoskie, founder of TOMS Shoes, Barry Sternlicht, chairman of Starwood Hotels and Resorts Worldwide, Stephen Hanson, founder of B.R. Guest Restaurants, and rapper/entrepreneur Snoop Dogg (no wonder every seat was filled!). CNBC's Maria Bartiromo interviewed the group and extracted some pearls of wisdom, relevant to all entrepreneurs, young and not so young alike:

1. Some Rules Are Not Meant To Be Broken. Blake Mycoskie talked about how thrilled he was when Nordstrom's first started carrying TOMS Shoes. He stubbornly refused the retail giant's request for the shoes to be packaged in traditional shoeboxes rather than the environmentally friendly canvas bags that Mycoskie was so proud of. Nordstrom relented, but the bags were a stockroom disaster: they couldn't be properly stacked, their drawstrings became tangled, and they caused frustration among the sales staff. The result: "We got kicked out of Nordstrom and it almost put us out of business," Mycoskie says. "Now we put our shoes in boxes." Lesson: choose your battles wisely; compromise isn't a dirty word.

2. Admit That You Don't Know It All. Stephen Hanson grew his restaurant empire from one location in New York (Coconut Grill) to 15 locations in three cities. But he didn't do it alone. Hanson relied heavily on experienced mentors in the industry. "I used to pick up Michael Weinstein every day at his home and drive him to work so that I could talk to him about the restaurant business," says Hanson. Weinstein is the founder and CEO of Ark Restaurants, which owns and operates fifty food-related businesses. Hanson's advice: seek out successful people who you admire and respect and don't be shy about asking for their advice.

3. Customer Research Is Overrated. According to Barry Sternlicht, when hotel guests were asked to name the ten most important factors to consider when choosing a hotel, bed comfort didn't show up on the list. "But when we asked them how much extra they would pay for a great bed, the answer was $20 a night," he said. And so began Starwood's successful campaign to differentiate itself to consumers through the quality of its beds. "Sometimes people don't know what they want until you offer it to them," says Sternlicht. He also offered the audience my favorite piece of advice of the morning: "People lose their fortunes when they lose their humility." Hear that, Wall Street?

4. "It Ain't Nothin' Y'all Can't Do." Those are direct words of encouragement from Snoop Dogg, who made my day when I got a great profile shot of him on my iPhone on the floor of the NYSE right after the opening bell. You can see it here. Snoop's advice: be original and creative and don't let lack of money discourage you. "I had to hustle from the ground up. I had no money, so I went to DJs and to parties until I met Dr. Dre," he says. And learn from failure, he adds, because "it teaches you what you shouldn't do." What did he learn? "I didn't understand when I first started out that I had to be a role model. I brought everyone up with me — the homies from the neighborhood and the criminals. But then I realized I had to change my whole environment." Now, he says, his most important project is The Snoop Youth Football League, which he founded to help keep inner city youth off the street. "It teaches them how to win," he says, "and how to lose." Biggest surprise about Snoop: he took calculus because "if you stop at general math, you're only going to make a general math salary."

So what's your advice to aspiring young entrepreneurs? What do you know now that you wish someone had told you when you were first starting your business?