if you haven't decided what you want and where you want it, don't get a tattoo. don't get tattoos that other people think are cute, get tattoos that mean a hell of a lot to you and say something about you. otherwise you are 100% going to regret it.
DONT get it on your lower back. That looks trashy and it seems one out of every three girls has em there. I got one on the back of my neck...an area that wouldn't sag and that I can cover up with my long hair if I have too. Depending on the type of tattoo, I think some look really cool on the top of the feet.
If you don't know what tattoo to get then don't get one at all...but the type of tattoo dictates sometimes where you should get it. Don't get the tramp stamp...but some good areas for girls are the back or the leg.