Part IV- Do your homework and ask educated questions. Prepare your questions. The shop's staff will respect you for being a good researcher and consumer.
A reputable shop should be willing to explain in lay language-and even show you what's going on with your car.
If the owner or mechanic is annoyed by your questions or talks over your head, he or she may be trying to intimidate you, sell you unnecessary services or overcharge you. Find a new shop, pronto.