Kevin O'Leary of ABC's Shark Tank says tip $20 on top of your original tip

• “If you're going to go to a neighborhood restaurant more than once, tipping is an investment because you want to establish a relationship with the waitstaff to take care of you. That's been around as a rule forever. ”

• “Here's the way I look at it. If you're investing in that place and want to establish a relationship and you get great service ... put a bill, a $20 bill down [on top of your original tip]. It's a crazy amount of money, but you're showing respect.”

• “When you give cash, generally speaking, that's theirs and you're showing respect that they don't get from anybody else. You're saying to them, 'You were great to me. I want you to remember me, I'm investing in you,” he explains.