Something I heard that makes sense: If you're thinking of getting a tattoo, start by going out and buying a shirt that you really, really love. Something that represents who you are and makes a statement about your life. Wear it every day for two years. After that, if you still love the shirt, you've shown that you remain attached to things -- get the tattoo.
Seriously, I'm mid-40s, and most of my same-aged friends who have tattoos regret them. I know a number of people who've had them removed (or who are saving up to have them removed).
As someone else said, they tend not to "age well", so consider that seriously. And remember, too, that you'll need touch-ups periodically, so this is not a one-time cost.