My own experience is that you should start small. You can always add, but its damned hard to erase.
It's kinda fun if you put a detailed tattoo in a somewhat "private" spot. Gives you a legit excuse to show it off, and that can be fun. With fine details, most will have to look closely, and take their time at it. Years ago, I had the head of my penis tattooed. Been lots of fun at parties!
You can have a tat removed with a laser, but its expensive.
The pain factor can be addictive. One of my best friends owns a tattoo studio, and he explains that the experience triggers an endorphin rush. That in itself can be habit-forming. Lots of people go on to "play piercing" to get the same rush. No problem so long as you keep everything clean and sterile.