My suggestion is that if you don't know what you want and where and why, then don't get one. A tattoo shouldn't be something that you think looks cool at the moment, it should be something you've considered for years, and that has a personal meaning to you. I've been tempted to get a tattoo for a while, and i've already drawn the picture, but i'm going to wait a couple of years and see if i still want the same picture then, and if it still means what it means to me now. It's going to be there for my whole life, so i'm not planning on just randomly getting something that i think is cool, just to regret it for the rest of my life after a while.
My sister's tattoo rules. She draw it when she was 16, and she's 24 now and is going to get it done soonish. Though i think she's making a mistake with changing the letters on it. It's got the first letters of her name, T.M, but now she's getting married and changing the M to an L because of her new name. I think she shouldn't do that, because she might get divorced and get married again and stuff, so...
I also wouldn't get a giant tattoo, because if i started to regret it a smaller one would be easier to ignore and hide. Erm..I'll stop rambling now :shame: