Make them deal with consequences. Most kids have plenty of friends, there are times they need a parent, if they need a parent and you are a friend they will go elsewhere for advise. Be a parent, not a friend. You cannot be both. Parents are not cool, they never have been, they aren't suppose to be. Kids need rules to feel loved. If you don't care what they do, they think you don't care.
Most of us had a blast as a teen, but would never want to live through the emotional crap. It's was pretty intense at times. Remember that.