Try
http://www.flylady.net
If you do exactly as she says, you WILL be able to get your teenagers to look after their rooms properly. It'll take a while and you won't believe it all at first, but it is EXCELLENT! I have been using Flylady since last November and yes OK my daughter is only 8, but she's going on 15 and these days her bedroom is so immaculate it puts mine to shame!!!
Flylady suggests breaking the room down into 'zones', i.e. clothes, floor, desk, books, etc. and giving the child 15 minutes a day to do one zone. If they're not done after 15 minutes, it gets left for next time. It's amazing how much can get done in 15 minutes. If my 8 year old can look after her room, so can your teenagers. (Oh and my daughter's room was such a mess before, you couldn't even get the door all the way open!)
Imagine if someone came and told you to tidy up all your mess or you wouldn't get to do something you wanted to do. You wouldn't know where to start, especially if that person had given you a time limit. You'd be fighting a losing battle, getting stressed out and unhappy because you'd miss out on something good. According to Flylady the room didn't get that way overnight and it won't get clean overnight either.
If YOU get into flylady's ways around the whole house, your kids will eventually notice and start to do some of the things you do (saving you from doing it, imagine that!)