The best advice I ever received on this subject was that 90% of classroom behavior problems come from poor planning by the teacher. As earlier posters have proclaimed, your entertainment savvy and dramatic flair will make a difference, and having a full and varied plan for the entire class will satisfy most of your students. Meticuloud planning will prevent most problems. This is easy to say, of course, and I didn't succeed all the time, but it was easier for me to explain breakdowns afterwards. Plan the class in short increments, to match the teenage attention span, and once they trust that you will have an interesting and relevant class, most of them will follow just fine. As for the other 10%, these are merely a[xx]holes who sadly will one day rule the world.