We use I care language: We don't call names, or do things that hurt other peoples feelings, on purpose.
Hands/feet are for helping, not hurting. No hitting, kicking, etc.....
We are responsible for what we say and do. I don't want to talk about what Susie was doing, we are talking about what you did right now. I'll talk to Susie, when we are done.
We listen to our friends. If someone is speaking to you, you listen to what they have to say.
It takes A LOT of work, and talking, and reminding, and sometimes a timeout if they just insist on being ugly, but also alot of praise if they remember to listen when someone is talking to them. It does work, if used consistently. I see children in the K room that have been at this center since they were two, and much of the time they can work their own problems out, because they have learned the skills to talk to each other.