I have both a tat and a piercing. My tat is in a spot where no one will ever see it unless I want them too. I think it's best to make sure that if for some reason in the future you don't want people knowing you have one - then put it where it will be inconspicuous. And no, it's not a temporary insanity thing. It's a I want it so I'm gonna get it thing.
Mine is a tribal star - kind of a star with a fluer-de-lis on the end of each tip if that makes any sense right on my tail bone. It hurt like Heck, but I love it... and so does my husband! It's solid black.
In my teen years I wanted a Bird of Paradise (the flower, my favorite) up my side... the stem going up my waist with the flower spanning up and across the side of my breast... in full color of course! I decided that the concept was all good and fine but the hiding would be more difficult and what would happen when I had a kid - the stretch marks and stuff (not that this is a concern for you!) So I went with the tail bone and a cool star.
I agree with the thought of don't do something too meaningful now, because all of that stuff changes as we grow and mature. Even if you are 40! Do something that is undoubtedly cool in your mind. Color fades with time but black doesn't as much. It's gonna hurt more if you do it over bone than the fleshy area's but it doesn't last for too long. Make sure that you go to a tattoo parlor that you trust. I went to the best in town. It was very clean and very professional.
DO IT! It's YOUR mark. No one else has your mark (unless your one of the Hell's Angel's and getting the mark of the club!) it's a sign of you!