Nevertheless, many pseudo artists steal pictures from other artists and show them as part of their portfolio, so this last step won't be of much help by itself. You need to find out if the artist(s) you are interested in are really what they say they are, and the best place to do this are the forums.
Tattoo forums usually have many experienced members that can give you reference about a specific tattoo artist/studio, and recommend you others well. This reference could be vital to make a decision as long as the forum user knows what he's talking about. Many people (mostly inexperienced) could think a lousy tattoo looks great, which is exactly the kind of advice you want to avoid taking. Get as many opinions as you can, and check the reputation, number of posts and profile of the people giving them.
With all this information you're ready to make some calls. Pick up the phone (or go personally) and talk to the preselected artists. Chat a little about your idea, what style you want to get, which are the possible spots in your body, what should and what shouldn't your tattoo have, what colors you would like, etc. Ask a little about the procedure and what sanitation measures they take. These steps are of vital importance, because you must feel comfortable talking to your artist; if you don't, then you may consider other options. On the other hand, avoid any studio that lacks taking appropriate care of hygiene.
Having done all this, you can consider yourself ready. If you don't have a design yet, you can let the artist create one for you (this is usually the best recommendation, given that real artists are experts in this field). Artists charge for their time and designing a tattoo takes time. But considering this is something you'll wear for life, you better be ready to spend some money in the designs as well as in the tattooing process.