Granted, most mechs are capable of turning a wrench, but there are still a ton of guys out there that could FUBAR a chevy water.
Being an ASE Master means that you have taken all 8, not just taken more than 4.
I'd look at the guy, more than ask a ton of questions. How does he appear? Shirt untucked? Grease up to his elbows? Does he lean against customer's vehicles? How does his work area look? His tool box? Really, the point is, if he takes care of himself, then he'll take care of you and your vehicle.
Then the typical stuff. If he's wearing an ASE Master patch, then he's proud of it. If the shop is displaying his certificate, then they're proud of it too. Ask if they have access to All Data, or at least an outside source of information, if they happen upon something they're unfamiliar with.
Lastly, and I know it's kind of biased, but what do they drive! An old arse beater or a nicer vehicle. If they're taking care of they're own stuff, or take pride at least in they're vehicle, then that reflects their own belief system. That also translates into how they work. They didn't get there by being sloppy, moving from shop to shop searching for more money, or running away from a constant chain of messing up vehicles and getting fired.
Lastly, what beer do they drink? Because when they do a good job, a 6'er on the tool box is always a nice pat on the back. That way, they remember you, and will continue to treat you with the respect that you demand. If it's an Infiniti tech, they might drink wine.
