I work at a small mom and pop Canon dealer camera store/mini lab/photo studio, and all of the fellow employees (I think there are maybe 12 of us) are photographers and know a lot about photography. I've had many people request to talk to me when getting prints made, looking to purchase new gear, or even just wanting to say hello because I've been so nice to them and I know what I'm doing.
Yes, I do get a commission when I sell stuff, but I'm not going to try to up-sell anyone. I get down to the point - whats your budget? how much gear do you have/what gear do you have? are you looking at getting any more gear in the near future (in reference to camera bags and needed space)? Do you shoot sports at all? if so, inside or outside? etc..
There was a guy that came into the store, he was a photographer for the newspaper in my town. He said "I have two D700's..." and I think 5 lenses as well as 2 flashes and some other stuff that he needed to have on him at all times, and have easy access to. I said, "did you bring it with you?" he said, "yep its in the car." I had him bring it in, and we tried it in about 5 different bags, customizing them to fit his gear in them so that he got the best fit. He ended up going with a Tamrac Cyberpack 8 - our nicest bag. I didn't try to up-sell him, its what he needed for his gear.
oh yeah... and I'm 18 started working at the store when I was 17. (not related to the store owner or anyone there) everyone else that works there is 25+ Don't judge the salesperson - sometimes we actually do know about what we're selling to you 
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But I do have to agree that some salespeople at other stores are idiots, and alot of our customer's don't know jack about photography, you just have to tackfully tell them they're wrong 
