What I did when I was looking for a place to get pierced was visit a few of the shops I heard of. I'd go in and talk to the owners, look through their books and ask them general questions. I'd go on a low volume day, meaning not alot of people around.
I would ask them about their shop, procedures, get to know them. I had visited at least three shops, and the first thing I would take notice of is their cleanliness. Following shortly after would be good PR skills. I don't like jerks, it's bad for business anyways.
I wouldn't want to go to a place that I would feel uncomfortable. I continued visiting this one parlor for a while, and got to know the people who worked there, as well as their regular customers. So when I finally got the courage to go in and pay for a labret, I was confident in the people around me. They made it quite enjoyable, and since they knew me a little, it wasn't that bad.