Read the children a story about a conflict and how it was resolved. Stop reading before the solution is announced and ask the kids how they would solve the problem. There are many books available on this very topic, often starring characters, such as Winnie the Pooh, that the children know and identify with.
Present a play. Have two or more students act out parts after you've coached them. Have them stop before resolution and have the class suggest various ways to resolve the situation. Discuss the better ideas with the class and ask which one they think is best. Have your actors act out the resolution. Children have a finely tuned sense of the concept of fairness, and being able to decide on a fair solution will produce consensus that will carry over into other class activities.
Sing a song with the students about solving spats, and have them sing it every morning for a week until everyone knows it by heart. Songs can be found on teaching resources websites.
Teach conciliatory language that addresses a problem without escalating it. Saying "My feelings are hurt when you do that" is much better than "You're a bully who hurts people's feelings." Kids should start sentences with "I" or "My," not "You." Have the kids come up with examples from things that have happened to them in the past.
Use an actual squabble in the class as a teaching moment. Have the children start the argument again, but this time playing each other. This will teach them a degree of empathy and, in the act, make the argument seem a bit trivial. Have each student involved stay in character as the other and suggest a solution to the disagreement.