Talk to students often about classroom rules, procedures, rewards and consequences. You may have all these posted in the room, and you probably discussed them during the first few days of school. Don't stop there. Remind students of certain rules when you see that a problem may be developing. Review rules after holidays like Thanksgiving and Christmas when school is usually dismissed for one or two weeks.
Use a simple behavior plan with clear objectives that are easy to remember. A long list of "dos" and "don'ts" will go unheeded for the most part. Adopt three or four rules that encompass all aspects of the classroom. For example, "Raise your hand before you speak," "Keep hands and feet to yourself" and "Come to class prepared" address issues of respect for the teacher and the other students.
Establish an atmosphere of mutual respect in the classroom. Greet students when they enter the room, make eye contact and give them a word of encouragement. If a student misbehaves or becomes disruptive, do not yell or argue. Ask him to get back on task, remind him of the consequences and continue teaching. Most of the time, this will diffuse the situation. If you must send a child out of the room, do so calmly.
Determine that every day is a "new day" in terms of dealing with students with repeated behavior problems. This does not mean allowing students to take over the room or get away with offensive behavior. Instead, it means starting the day with a clean slate. Do not bring up a child's past mistakes or make reference to the fact that he deserved to be suspended or placed in detention. Do not treat students as if you are just waiting for them to get in trouble again so you can punish them.