My son is grown and in college now and so doesn't face that problem any more. But when he was younger, time-outs worked like a charm. We had a spare bedroom that was very sparsely furnished. No computer. No TV. No nuthin. That was the time-out room, and it worked to help isolate him (briefly) and let him calm down and re-think his behavior. He didn't need that very often, but he's an only child and was very accustomed to getting what he wanted. So there would be times when we'd have to say no, and he could be very dramatic. Time outs are the way to go. I don't believe in hitting. I wasn't hit as a child, and I never struck my child, either.

When he was a teenager, we removed privileges when we needed to discipline him. He'd have to stay home and not go out and do stuff he wanted to do. Once we removed driving privileges when he was 16. Once he lost the use of his PC. Usually once was all it took, and then he'd toe the line.