I whole-heartedly agree with everything that's been said thus far. However, there are a few things I'd like to add:
-First and most important, in my opinion, If you're thinking to yourself, "I want a tattoo, but I don't know what to get” You might not want to get one just yet. Tattooing is a great experience, but only if the art means something to you. Your art is going to be with you a long time, and be sure your kids (nieces, nephews, God-kids, ect.) will ask what they mean. Do you really want to have to answer, "Betty Paige is hot...and she dances when I flex"
-Flash is great to firm up the design you have in mind. But if you walk into a shop, choose a design off the wall and 5 minutes later your in the chair, you'll probably regret it.
-It's been stated that if you lack artist ability (like me) most tattoo artist will happily listen to your ideas and draw something up for you. This collaboration between your artist and yourself can be very rewarding. Remember, if they are a good tattoo artist they want your design to be perfect just as much as you do. If what they draw isn't quite what you had in mind, tell them what you see differently. Naturally, be polite though.
-It's my personal belief that if your artist creates a custom piece for you, and really works hard to get it just right for you, they deserve a nice tip (above what you'd normally give them for the tattoo itself). By creating your artwork, they've given you something very special, it's nice to reciprocate. If you are an amateur chain mailer, make them a little bag. If you are a photographer, give them a picture. Of course if you don't feel you've got a talent, a nice batch of muffins or something does quite nicely too.
Enjoy your tattoo, and the process. I’d start saving now, because they are addictive and if you’ve followed the advice from everyone you’re more than likely to be back.