Restaurant tip trick.

Our system automatically assigns an 18% gratuity for parties of 6 or more, even if they want split checks afterwards.

So, when I bring the bills out, I point that out to people, telling them that "our system" does that and "I just want to let you know, so there's no confusion."

And, a lot of times, people add on a lot more in tip on top of that, to the point where you're making like 23-25% on the bill.

"Oh, he's so honest," they must be thinking.