What I did notice this weekend while we were away camping is that the quarreling practically stopped.
The moment we entered back into our home - it started up again.
I do try to redirect their quarreling and model more appropriate ways to say what they are saying... and I make them repeat it after me to practice. heh.
Sometimes, I just let them work it out themselves. If they can't work it out - whatever they are quarreling about becomes mine for awhile.
I realize that they need to grow into proper communication and that some quarreling is developmentally appropriate... but I still can't stand it.