Whenever I am dealing with a local store, I always deal with the owner so there is never any commission issues. If I am seriously looking at something, I will make sure they can have it set up when I get there to save time. If they are a one person operation, I will make sure they will be there regardless of hours posted if I want to stop by (doesn't happen nearly as often as in the early 80's). They have lives and go to doctors, etc. and occasionally stray from the hours.
If you make your intentions clear, you will earn their respect as you won't waste their time. I see the value in buying from a local guy for support and expertise. They can give you an educated opinion, and you can learn usually. The ones that are surviving are in low overhead spaces they either own or are very low rent.