Our shop in Kansas City we found out was constantly being reported to the "Call For Action" team at a local TV news station, several times they sent in a "test car" to find that we would make an accurate diagnosis, repair it correctly and for a reasonable price.
A danger sign that I found to look out for was if a new customer came in and talked about how the last garage he was at is a bunch of idiots, just out there to rip people off. I found that they would always leave dis-satisfied then add our name to his list of incompitants then go off to the next shop down the street.
Vendor Caveat!