What I do....is say firmly NO OUCH. THAT HURTS. Then put him on a time out. Bottom step or a chair close by but away from everything. After his time out is done, two minutes, then u take him by the hand to the child he bit and say "no biting. Ouch That hurts. Say sorry." Then he goes to play after he says sorry. Do this every single time. He will start to connect the word no ouch and time out together and realize it's not a good thing to do. He will then get it. But u need to be consistent. Everythime he bites or hits. It's no ouch and on a time out. I've done this method many ways and it always solves itself after a wk of times outs all day . Good luck.