Teens need boundaries that need to be enforced. At the same time, they need some leniency so they can feel somewhat independent or that they have a say. For instance, if you say, "Okay, it's New Years Eve. You can stay out til 1 am instead of 11 pm tonight." They like to negotiate and win a battle once in a while, so they don't feel like you're controlling their every move. You, as a parent, can plan these battles ahead of time. If you know an important date is coming up for them, you'll know ahead of time that you're going to let them win this one, just make sure you let them plead their case first, so they feel as though they've accomplished something!
Teens are a bundle of raging hormones. Everything that happens to them is the worst or greatest thing in the world. There's no in-between. When they're going off about something, try, "Ya know, that happened to me once....". (You know it has!) You'll be surprised at their response.
Parents are not cool, so don't try to be. The only thing teens have to say about parents is, they're either dorks, or they're really nice. The cooler you try to be, the dorkier you are, so go for nice.
Tell them you love them. These are very trying years, and your patience wears thin daily. They are defiant, and they would rule the world if they were elected, because they are all-knowing, but at the end of the day, before you turn in for the night (if they've come home on time), tell them you love them. Even if they didn't come home on time, after you ground them, tell them you love them.
They need one constant, never-changing thing in their life: Your Love. Tell them you love them. By the time they're 25, you'll be their best friend, going to happy hour together after work, and cool. The best part is, not only will you still love them, they'll love you back.