had better (do something)

Should. You had better listen to what I'm saying before you get yourself into more trouble. Oh, Mom told me last week that I had better start my book report—I just didn't feel like it. You had better keep your mouth shut—the boss doesn't look kindly on people squealing to the cops.

had better/best do something

used to tell somebody what you think they should do: You’d better lock the door before you leave: there are lots of thieves about. ♢ Hadn’t you better check to see if the baby is all right? ♢ ‘Shall I phone her now?’ ‘You’d best not. She might be asleep.’