Step 1 – Take your car to multiple repair shops for inspection.
Let's say that your car is making a loud, metallic grinding sound every time you push on the brakes, so you take your car to the local repair shop you've passed a day in and day out on your way to work. The first thing you should do is let the service writer know you are here for an inspection and to not perform any services until you have had the chance to authorize them. Ask them to inspect your vehicle and quote you a price. If the service writer comes back to you after the mechanic has performed the inspection and says your car needs additional repairs, this might be a red flag. Keep in mind that when a service writer comes back to you with additional repairs he is not necessarily padding the bill. What you need to pay attention to is how he or she explains the additional repairs. If the service writer goes into great detail about the necessity of the additional repairs only leaving you to forget why you bought your car in for inspection in the first place, be weary. Take your car to another auto repair shop or mechanic for inspection. See if they come back with the same result. I would do this until you feel comfortable with the repair shop and / or mechanic.
Step 2 – Do not let the repair shop or mechanic put your car on the rack and start taking it apart until you give them authorization.
If you fail to do this you might be forced to authorize unnecessary and costly repairs just to get your car off the rack. You might be forced to pay a large fee to have your vehicle reassembled. This is not a good situation and one you unfortunately want to avoid.
Step 3 – See how the service writer explains additional repairs.
When you bring your car in for an oil change / inspection and the service writer hits you with a list of additional repairs. If he or she talks about the additional pairs and the importance of them only leaving you to forget why you bought your car in for work in the first place, this might be a red flag. Not all mechanisms are evil and try to take advantage of you, but keep in mind of this situation.
Step 4 – Ask the repair shop and or mechanic to itemize your repairs.
Tell the service writer to include parts pricing and expected labors hours. If they fail to give you the itemized information something could be up. If they do give you an itemized bill you now have the opportunity to do some research. Go home and try to find out as much as you can on the expected work, or better yet, take your itemized bill to another repair shop and ask them to look it over.
Step 5 – If you are taking your service that includes tire rotation try marking your tires (discreetly of course).
For example, mark the front tire on the driver's side with the number 1, and then mark the back tire on the driver's side with the number 2 and so on and so forth. Snap a picture with your camera phone (assuming you have one) or digital camera for documentation. When you pick up your car from the repair shop, prior to paying the bill see if the tires where rotated. If they were not rotated you have proof that something is wrong and you can be assured the repair shop is not going to try and mess with you from that point on.