Finding a good mechanic

When I was a young boy after school I would go to my Dads full service gas station and help out by waiting on customers, tracking inventory and sales ect.. etc.. watching the grownups in action was certainly an education in itself. they would take turns playing good cop , bad cop with the difficult customers witch always led to a sale and a return customer.
the mechanics that worked strictly commissions on the other hand were totally ruthless when my Dad and his partner were not around! If a well dressed customer in a nice car , when they checked the oil they would spit on the dip stick and tell the customer that head gasket was gone because the baubles on the dip stick were due to water mixing with the oil. then they would rent the mark a loaner, and keep the car for about to weeks,mean while they`ed get a engine head ( the part of the engine that has the serial number on it from a junk yard , clean off the head and the customers engine install the junk part and paint he engine and head then collect a fat payment for replace the engine.
When ever I purchase a car, first I check the fluids to make sure that nothing was added to the engine or transmission to enhance or alter the cars performance or cover up a knock in the engine if I purchase the car I`ll buy the shop manual for the car so if I have a problem, I can fix it or at least be able to tell if a mechanic is trying to put one over on me. As Mr. Sims, used to say an educated consumer is the best customer.