My son CAN be this way. You need to intervier less. If he hit someone take him away by the hand and say "no no" and (I take my son in his room, I walk in and say "you stop that" I actually close the door and let him yell. When he stops or it's been about 10min AND i can walk in and he stops I let him out. I do this for everything. I don't say "NO" often I say "no no" calmly.I don't yell, I don't yank him around I stay very calm. I tell him "No no" and if he won't i take him by the hand and move him from what ever he's doing very quietly. Now if he won't move or doesn't allow me to walk him away, I pick him up under his arms and move him. But I do it calmly. If he starts throwing a fit I take him by the hand or under his arms and put him in his room. As I said before. But I NEVER get mad, I never yell. If I'm in a place i can't put him in his room, I move him somewhere he can throw him self around and I lay him there and let him do it. lol If he runs I pick him up under his arms and let him throw if fit just 2 or 3 in off the floor..He will get over it quickly if your not getting any more involved.The reason he's doing what he's doing is becuase he's putting on a show for you. He's figured out how important it is to you by how involved you get. My son is also 20 mo. I also have an 8yr old and do childcare out of my own home, My sister also does childcare in this age bracket and has 3 boys of her own. So plenty of experance here..