Separating them when they do, no matter who started it, is very helpful. If they are younger, they want to play with each other. If you send them to their rooms each and every time they start this stuff, then after a week of you doing it INCESSANTLY, they will start to police each other (like one saying to the other "Don't argue or mom will separate us!")
However, if you find that one child is trying to boss around the other kids so that the other kids don't seem to get a say in anything, separate THAT kid so he or she doesn't get "too big for their pants", so to speak.
You have to give them a consequence that is swift and consistent, and I believe that this is the best one.
By the way, when they are given this consequence, NO TV, no electronics, no computer. You want them to be bored without each other.
Dawn