Nothing wrong with mates rates. Lol. I try for those all the time.
Otherwise I look for cheap and convenient. Honesty would be nice but you don't know that until you have been there.
On a new car, I generally go back to where I bought it, which is neither cheap nor convenient. Protects the warrantee. Except sometimes the first service or two is covered in the deal. My Mini Cooper covered 2. The Subaru covered none, but it had a recall that did one. The new Jeep has 3 I think. All of them required a drive to the next city.
So, after that, it depends on what I need. I go to where it can be done locally, and is cheap. Oil changes, I just go to the auto parts store and by the oil that I want and the filter, and then go to walmart auto to get them put in. I change the air filter myself. Any other fluid change I take to any garage that can get it done quickly, while I wait. Tire and brake stuff goes to the tire store, Batteries have to go back to the dealer because after it has been changed, the car needs to be reprogrammed to act like it did before.
Cars are such a pain.