"Shark Tank's" Kevin O'Leary hates wasting money. For example, he refuses to spend money on a cup of coffee when he can brew it at home.
"Do I pay $2.50 for a coffee? Never, never, never do I do that," O'Leary tells CNBC Make It. "That is such a waste of money for something that costs 20 cents. I never buy a frape-latte-blah-blah-blah-woof-woof-woof for $2.50."
But O'Leary is willing to shell out a few extra dollars when there's a potential return — like when deciding how much to tip.
"If you're going to go to a neighborhood restaurant more than once, tipping is an investment," O'Leary explains, "because you want to establish a relationship with the waitstaff to take care of you."
O'Leary says this if he goes to a place two or three times and decides it will be on his regular roster of eateries, "I introduce myself to the manager and ask to meet the owner. And from that day on I tip 20 percent, never less."
But he also has a trick to really stand out. O'Leary's number one piece of advice is to add an additional $20 in cold hard cash onto your tip, just once, on top of paying the full percentage.
"If you're investing in that place, and you want to establish a relationship and you get great service ... just this one time throw $20 down," he suggests. "It's a crazy amount of money, but you're showing respect.
"You're saying to them, 'You were great to me. I want you to remember me, I'm investing in you," he explains.
"This is old school stuff, but you form a bond with the team running the establishment that is very valuable."
Etiquette experts at The Emily Post Institute say the appropriate amount to tip is 15 to 20 percent, so adding an additional $20 on top is well beyond common courtesy. But in the U.S., where many states allow restaurants to pay tipped employees less than minimum wage under the federal Fair Labor Standards Act, it's sure to be noticed.
So the next time you're headed to your favorite restaurant, consider stopping at the ATM.
"Cash is king when it comes to tipping," O'Leary says. "That's an investment. Try it sometime, it goes a long way."
Don't miss: This simple tipping trick could save you over $400 a year
Like this story? Like CNBC Make It on Facebook!
Disclaimer: CNBC owns the exclusive off-network cable rights to "Shark Tank."