When they are old enough, they will be punished with calisthenics and confiscation of favorite items/deprivation of favorite treats. When they are little, I will probably hit them on the wrist or swat them on the bum and say "No!" or "Stop it!" loudly and firmly if they do anything wrong. There is nothing wrong with hitting (not beating, mind you, just swatting once or twice) little kids when they are doing something danngerous or otherwise unacceptable.They cannot really understand reason until at least 4 or 5, and need to be trained not to do things much like like animals.