The bike shop I use (Cambria bikes in San Luis Obispo ((shameless plug))) has two things going for it.

1) Great service
2) A coffee shop

Those aren't the only two things... but they're important. One thing you need from a bike shop is that they stand behind their work/product. Anyone who sells you one thing one day, and then calls it crap the next day when they try to sell you something else should be avoided. When parts from the bike I bought broke (chainrings bending well before they should) they were replaced with better quality parts, got a free tune up, and done in 2 hrs while I went to the movies (on a drop in basis).

Good shop.

Best advice though is to look around your area. Don't hesitate to try a different shop if something seem odd about the one you're using.