Finding a decent artist isn't too hard these days. Go to an established shop that has been around for a while. Ask to see the artist's portfolio. If they don't have one, don't get a tattoo from them. They either suck, or are brand new. If you like what you see in the portfolio, go for it.
Checking for cleanliness is pretty easy. Ask if they have an autoclave on sight. If they don't, don't get a tattoo there. It doesn't make them unsanitary, but it makes it more difficult for them to sterilize their equipment, and they will be more likely to use less than sterile needles.
Also spend some time chatting with the artist. This person will be leaving permanent marks on your body. You don't want to look at your tattoo and be reminded of the asshole who put it there.