By me, the easiest way to judge an LBS is by checking out the pictures the mechanics and sales guys have hanging in the shop, or find out about their involvement in the local cycling clubs:

SVC (my favourite shop) has pictures of the shop staff in races, or photos of the teams the shop staff are on. Posters are mostly famous race pictures, or just old advertising banners from the shop. The guy who co-owns the shop is the president of RUSA and the local randonneuring club.
I find that kind of fanatical dedication to the sport/hobby/lifestyle (whatever you want to call it) really brings a high level of service no matter if you're going in for a 3 hour fit session and a $7000 racing bike, or a $400 setup to ride a few miles to work.
I've had one of the shop guys pass me going up a long hill, him on a training ride and me just commuting home, slow down and ask me how I'm enjoying my new bike.

It's not just bike shops where you should shop around until you find one where you'll get the best service. I had a bad experience with an electronics purchase this weekend. Went into one shop, had to ask twice for someone to come and help me, and 5 minutes after the second request I left the store without buying anything because no one ever came to help me out. At the second shop I had a sales rep ask me if I needed any help within 2 minutes of checking out a few components.