Check out books from the library that have a conflict resolution theme. Read the books aloud during story hour and ask the students to state what they believe the morals of the stories to be.
Use a point system, giving students a point each time they engage in an argument. Make it clear that once a child reaches a certain amount of points, he will receive some sort of punishment, like a trip to the principal's office.
Put the students into groups and have them write a skit based on a common class argument, such as taking turns to use a toy. Have the groups perform their skits, complete with ways to peacefully end the argument.
Have the students write out their own conflict-resolution stories on sheets of construction paper. Staple the papers together to make a book of stories that the students can read aloud to the class.
Have an open discussion with the students any time an argument occurs in the classroom. Ask them how they think the argument should be resolved. This will get them thinking about ways arguments can be easily solved.