The best way is to ask people you know in the area. I'll just give you an example of what've I've done. I asked a friend whos worked on cars where I should go. He linked me up with a master honda mechanic that has a garage in his backyard. He helps me with major repairs but hes live like an hour away from me so for minor repairs I just took my car to a few shops close to me that had good reviews on google and I just tested them to see if they were trying to sell me shit I don't need or trying to rip me off. If you can do this with a few shops then you can find which one is the best and then when you have a repair or maintenance you can call a couple of those places and see how much their trying to charge you to see if your shop is on the level.  

A few years ago, the "Car Talk" show on public radio had a web site where people discussed their car questions and problems, just like this. They had a mechanic rating things, kinda like Yelp reviews.

I'd give a few bucks to Patreon to help start something like that here, how about you?

Lol.  Great idea!  "Scotty Approved".  Now we need a logo and franchise agreement.

Be leery of any place that hands you a detailed list of all the little problems with your vehicle.

I you tell them to "check the clunk in the right front", and they come back with an estimate detailing the clunk, but also 12 other issues (that have nothing to do with the clunk) .... big red flag.

I'm sure Scotty could tell you which mechanics NOT to visit. I think he sees a lot of cars that have been worked on.

When a mechanic is good you can tell because you don't have to visit him very much.

I’ve almost always heard Scotty say avoid dealership. I completely agree. The Toyota dealership I take my 4Runner to is very expensive. And their work is subpar. 

So I looked it up, and the Car Talk Mechanics File is still out there, though the show has been off the air for a few years. FWIW, here's the link:

https://www.cartalk.com/mechanics-files