Generations of parents have always said that it seems as if their teenagers are speaking a different language. Teens have usually agreed and are usually happy about it. They don't want to be like their parents, after all.
It might be a good idea for you to learn to speak the language your teenager is speaking. These days it includes Urban Slang, Facebook, MySpace, and texting.
Get yourself some social networking action. Sign up for whatever social networking site your child is using. Chances are she has both MySpace and Facebook accounts.
You can be "friends" with your teen, which will keep you up to date on social activities she may have "forgotten" to tell you about, and it is a very revealing way to see the company your child keeps.
When you hear jiggy new slang words, look them up in the Urban Dictionary. Seriously. A lot of this language bending is clever and funny, and you'll be able to get the social references teens are using to define their collective sense of humor.
If you don't know how to do this already -- learn to text. If you do, you open another door for communicating with your child when she is away from home. Texting, although odd, is fun, and if kids can receive texts in SCHOOL, there is no excuse for your child to not be able to text you when she is out with her friends on a Friday night.
See their movies. Sure a lot of it is smut, but knowing what your child ingests through the media will help you develop wisdom in how to guide them through this media maze.
Remember, it probably won't be "cool" if you actually speak Teen when your teen can hear you, especially when said teen is around a group of friends, but it is good to know the language. It will keep you connected.