I never had to go to an auto shop as a customer but I went to several bike shops before I found 'My LBS'. Someone recommended a store to me so I went in there with cash in my pocket to buy a bike. This was probably 1987? No employee would acknowledge me and I browsed bikes for some time. Finally I just left. At another shop the guy was very helpful, pulled down every bike I wanted to see, put pedals on them, etc. I bought a bike from him but later found the shop I dealt with for 30+ years. This guy gave me deals on everything and treated me like a friend. He thinks I sent him a lot of business. I tried. He retired in June. Frack.
One time I needed a tire for my mtb and went to a shop near home. The guy seemed very annoyed that I was even there. I told him what I wanted and he pulled some wire-bead bike path special. No, I want a real mountain bike tire. He was such a dick I never went in there again.
I think so much of business is just common sense. I dealt with a big auto parts store when I worked at an independent shop. We were one of their smaller accounts, I'm sure. I went there looking for a part and the counter man said they didn't have it and didn't know where to get it. I was leaving and the owner of the store asked me what I was looking for. He studied it and remembered they had ordered one for someone else and they hadn't picked it up so he sold it to me and ordered another. He spent his time with me and probably only made a couple bucks on that part but I was impressed with his service.
I bought a used motorcycle from a shop and when I needed a part, if he didn't have it he would pull it off of a bike on the showroom floor for me.