I think the best thing you can do is go into the shops, see their portfolios, and talk to them. While you are in the shop, look around. Is it clean? Do they have their certificates on the walls? The internet can also be your friend. I went on word-of-mouth for the shop I went to, but also did some research on the net. They were very well reccomended, are involved with tattoo conventions in the areas, and had nothing but awesome reviews...
That said, I still went into the shop, talked to them and when it came time to do the tattoo- the guy I had was wonderful. Was extremely friendly, made sure to tell me that at any time I need a break, to let him know. Checked up on me several times knowing it was my first.
I am going back for my 2nd tomorrow. I pay roughly $100/hr ... price wasn't a factor for me. I wanted quality work, as it will be on me for life.
You want someone who will OPEN the needle INFRONT of you, so you can see it is a new one. Someone who gets fresh gloves before starting--infront of you. Watch them as they sanatize the area you'll be sitting at, their tables, their hands, and you.
There is a guy around the area that a lot of people tend to go to. He has the "$100-$150 as long as you can take it" specials. His work comes out great. Or it comes out horrible--depends if hes on or off drugs at the time...
Stay away from "tattoo" parties. While some may be reptuable, a lot aren't. Many BOIL the needles and re-use instead of getting a new one. They also don't tend to clean as good as they should--its an accident waiting to happen.