I've been very into Dexter (on showtime nit the cartoon), true blood, shameless, buckwild, and American horror story. I'm 14 and have been watching these shows since they started. Just depends on what your parents allow and what you're into.
My favorite show is greys anatomy, but it would be hard to start watching from where it is now. If you have Netflix, then you should watch it. Most parents would say it's not appropriate, but I'm 14, and I've been watching it for a while.