J.B.
My best advice is to take action. Don't just say no, put an action with it. Make it mean something to him... I have a 3 1/2 year old and a one year old... First, I tell him no, (for example, "No hitting!", then I put the one year old in his crib RIGHT AWAY. I leave the room and close the door. That way, he's safe, but I get my message across with something he does NOT want to do - be alone in his crib awake. He screams, and I open the door to say, "No screaming." He screams more... I repeat the process until he calms down... even just a little bit... he's usually still sniffing and huffing and puffing, but he's not screaming. This takes a few times before he really understands, but now all I have to say is, "Do you want to go into bed?" and he stops the behavior. It's not easy, but it works. Give it a try.