I'm in the process of getting my one and only - it'll take a couple of years and cover the entirety of my back when done, but I think it'll be the only one I get. My wife is convincing herself not to get the fourth.
I'll tell you the biggest issues with getting one little tattoo is that you really can't stop yourself from getting more - it becomes an addiction. The first is the worse because you expect all this pain and have doubts about whether you truely want it, but when you walk out of the shop you start thinking "wow, that wasn't too bad at all."
My advice is to stay away from "tribal art" and logos unless you REALLY like them. Fads change year-to-year and its tough to say what'll be cool in 20 years. One of my friends got a "Nike Swoop" logo chain-linked around both of his arms back in highschool, I wonder if he still has it.