P's and Q's
It's like telling a kid to say please and thank you. But with more swearing and less grace. P's = please. Q's = thank you. So watch your P's and Q's or you're a rude little brat.
Watch your P's and Q's, or I'll give you a wedgie.
If you don't say please and thank you, I'll eat your lunch.
Say please and thank you or I'll throw your phone out the window.