Hi fredhe12,

I would go by reputation, if someone is good it's going to show. I start by asking my friends who play who they go to and if a name keeps popping up that's usually a good sign. If you don't have anyone to ask locally I would do a google search or call the most reputable music stores in your area and kinda feel 'em out. A store/shop that is doing guitar repair is going to know how to setup your guitar correctly.
If a shop or person seems really busy and on top of their game, that's a good sign too, it means that a lot of people are using them.
If you go and see live local bands and they're good, I would ask the guitar player who he/she recommends.