Marcus Lemonis, entrepreneur and star of 'The Profit'
Best advice: Keep your word and do what you say you'll do.
"The best advice that I was ever given was about shaking hands and making a deal. Oftentimes, people think that the only way to make a deal is to sign a legal document — but if people want to get out of the legal document, they're going to get out of it.
"It sounds odd, but my mother gave me that advice. She said, when you shake someone's hand, you have to honor the deal that you made and you have to do what you say you're going to do. If you made a bad deal, shame on you — but that's the deal you made, so you're done.
"Actually agreeing to something with somebody has to mean something. On the show, 'The Profit,' all of my deals are initially done with a handshake. Ultimately, I do paperwork, but if you want to know what the movie's going to be like, watch the preview — and that's what the handshake looks like to me."