The first requirement really is to start thinking... hard.
If you are still reading this article and you still want a tattoo (thinking can work miracles you know) you should start with a basic tattoo theme. The themes which you should avoid when choosing are the ones relating to fashion. I don’t know if you’re aware, but once a tattoo is made it stays there, or at least it’s supposed to stay there.
Let’s say that you’re a big fan of ... err... 50 Cent. Such a big fan that you want to make a tattoo with his name. I don’t know if you’re aware, but ten years from now nobody will know who 50 Cent is and those who know will probably laugh their ass out when they see it.
Of course you could also look like an old school rapper who knows stuff, but why take chances? I have a friend who listened Guns’n Roses in the early 90’s and he made a tattoo with it. My God I really wouldn’t want to be in his shoes. There is no tattoo fashion or at least there shouldn’t be any.
Another thing you should avoid when choosing a tattoo design are names of loved ones. Specifically those of girlfriends or boyfriends. I know that this might come as a shock to you, but typically tattoos tend to resist better the time than love. Wives or husbands name are OK I guess, but caution is advisable.As a more technical tip avoid using designs that need bright white. This color is very difficult to obtain and may require many sessions and even then it tends to fade in time. Try using skin tone if possible, if such an alternative doesn’t exist you should avoid the design altogether.
Source : http://www.tattoo-designs.dk/choosing-theme-tattoo.html