Well, after working in a tattoo shop for 3 years and accruing 13 including a full back piece and some pretty intricate work I could give you some advice on them if you really want it. A few major points:
Avoid cheesy pop symbols - you never know if you'll like Tweety bird or playboy down the road and it just looks white trash when you are 40 walking around with cartoons on you.
Avoid bf/gf names: removal is just much more expensive than tattoos themselves and if you aren't married, or even if you are - man, you just never know. We've had more people come into the shop to cover names up than absolutely anything else.
Don't pick out flash on the wall - get your own piece designed. Everyone has those pictures on the wall that has no taste and doesn't realize 1,000 people have the same tattoo because flash is sold country wide by producers, not just to one tattoo shop. Custom work is usually more expensive if the tattoo shop doesn't just have a flat hourly rate, but you'll be MUCH happier with it in the long run.
No band symbols or names - big mistake.
If you are a professional avoid tattoos in places that may affect your job.
*** Everyone has that stupid celtic arm band - be original please, us ladies do not all think its hot, its incredibly unoriginal for expensive artwork (celtic knotwork = terribly expensive tattoos) and btw - the underarm is one of the worst places to get a tattoo in the first place.
Really when you get a tattoo its on you forever so get something thats meaningful, that nobody else has on their body, and isn't cheesy white trash, I think I'm a porn star or a member of Megadeath garbage and you should be ok.
Remember finally that everyone's answer to not getting a tattoo is that you'll hate it when you hit 80. If you live to 80 congrats in the first place but just remember, if you're going to get one, and you're going to hate it, at least know that its original and not something you went out and got when you were wasted (tattoo shops that are reputable won't get ya when you are drunk anyways or you'll bleed out) or because your friends thought it was a good idea.
I have a lot of tattoos, never considered getting one removed. Its all about thinking things out, knowing what is important to you in life (REALLY important - not a love for Bugs Bunny) and keep in mind good ones cost $$$$, they are there forever, and if its big - may take more than 1 sitting. Research your tattoo, research the shop, and don't listen to what people TELL you to get, think of what you like, talk to the artist, and have him/her draw something for you.