Act in turn

Check, bet, call, fold when it's your turn. Acting early gives free information and creates disputes. Keep your cards visible enough that the dealer knows you're still in.

If your buddy angles, slow-rolls for theater, or berates dealers, he will get worse games and worse lives. Ethics is EV: good players want to sit with fair players.

Acting out of turn gives free information and can bind your action. Teach your buddy: hands on cards, eyes on action, wait your turn — every time.