I would suggest using the timeout method also. I have 3 children 12, 9, 17mos. For the two older ones I put a chair in a specific place in the house and left in the same place all the time. I used a child size one. After I gave my child two chances of warning for whatever the reason then I would resort to using the timeout chair. They hated to be isolated away from everything fun. 20 months is not too young to discipline. I do discipline my youngest with the timeout only for a minute though. He is still not totally sure about it yet. He is starting to get familiar. It is better to start this early. They may be hard to handle at this age now but at least they will know they have boundaries later. I hope this helps. Good Luck