Explain and discuss classroom rules and consequences on the first day of school. Allow students to express their opinions and give feedback. This builds an atmosphere of mutual respect. Students are more apt to behave and work hard for a teacher they respect.
Apply rules uniformly and impartially. If students see you play favorites or bend the rules for a few, they will resent it. Although there are extenuating circumstances in some situations that call for a different approach, strive to treat students fairly.
Talk to students individually about misbehavior. Do not stop teaching and begin a shouting match with a disruptive student. Ask him to stop, then explain the consequence and continue teaching. If the student refuses or becomes aggressive, contact the office via the intercom system and request that the child be removed from your class temporarily.
Forgive and forget. That may sound trite, but it is important that the kids in your class see that you will not hold their mistakes against them. If a student commits an infraction and suffers the consequence, do not bring it up in class or refer to it in a derogatory fashion.