Let the argument simmer for a while, by leaving it alone, and avoiding communication. If you talk right after the fight, many things are said out of anger. However, do not wait too long, as allowing bad feelings to brew for too long creates a situation that becomes more difficult to make up. So after the fight calms down, make sure you talk to the person before it's too late. After you do that, sit down and say you're sorry if you are the one who caused the fight. Even if it was the other person's fault, just take the blame so you will make up sooner than later.