The BEST thing that always happened at my brick and mortar shop that I would frequent is HONESTY from the magician behind the counter. He would always tell me, "Rick, this is something you'll like and definitely fits your style." He would then demo the effect for me and if was something of a major purchase like over $150.00 he would show me the gimmick and make sure I would be happy with it. I know that sounds horrible but it helped develop a trust between us.
If it was less than that price and I liked the demo I normally bought the item. Also, there was always a sign up that said, No Returns, Once the item is SOLD, The secret has been TOLD. That made it clear to everyone making purchases that you knew there were no returns.
His shop was also wired for Internet demos on a computer screen if I was interested in something that he couldn't or didn't know how to demo.
There was also a back room where there would be lectures and workshops held about once a month which were open for general public to come in and pay a door fee.
Magicians could just stand at the counter and session but there wasn't any table.
One thing I hate when I have visited certain magic shops or dealers at conventions is that they "high pressure" you like a car salesman and you feel uncomfortable telling them, "No, I don't want that item."