I disagree with some of the posts.
A parent needs to give their teenager a lot of space and treat them like and adult. In other words, if your child is going to turn into a degenerate, you being an ****** of a parent wont change anything. In fact, by allowing your teenager to choose what their interests are, what activities they want to hang out with, and what they want to do with their lives will result in them being more motivated and responsible.
By allowing your child to be responsible, you wont have to hold their hands while they get their first job, sign up for extra curriculars, or apply for college. If you know where they are every moment, if you have to approve of EVERYTHING they do before they do it, you will probably get a strained relationship. Not to mention, they will probably do the things you dont approve of behind your back which is much worse, just to show you that you arent their dictator.
Anyway, the benefits of being reasonable and treating them with as much freedom as you would a colleague at work, you get an independent, self motivated son or daughter.
As a further note, assuming from how your question is worded, if you have kids that are about ready to become teenagers, look at it this way, no diapers, no throwing up all over the table, and no temper tantrums!... I like teenagers way more than toddlers!