Perhaps the most stressful thing about taking a car in for service is not the prospect of a big bill - it's the prospect of being taken. How can you reduce your odds of paying too much - or paying for a repair your car really doesn't need?

* Get a second opinion -

As with shopping for a car, rush decisions when it comes to authorizing repair work can come back to haunt you - especially if your car has developed a sudden problem and you feel panicky about getting it fixed right this minute. That can lead to a hasty decision - and possibly, an avoidable expense. A dishonest shop may also try to play on your obvious stress by over-stating the dangers of not getting the car fixed "right now."

Getting a second opinion before you authorize any work will protect your interests in two ways.

First, if both shops independently agree on the nature of the problem, you can feel pretty confident that the problem has been identified correctly - and honestly. On the other hand, if one shop tells you the car needs the entire transmission replaced while the other says the problem is a minor electronic glitch, you've likely just dodged a massive rip-off.

Two, if you get a second estimate your feel for what constitutes a fair price for the work will be much better. If the second shop's quote is much higher, you can go back to the first one - or ask the second shop why their estimate is so much higher.

If the two estimates are about the same, you can feel secure you're not being taken for a ride.

* Pre-shop repair shops -

For the same reason it's good to research the credentials and reputation of the doctor you're about to trust with your physical health, it's smart to research the credentials and check the reputation of a repair shop before you take your vehicle in to be worked on.

The two main things to look into are a history of consumer complaints (check with your local Better Business Bureau as well as the state/county office of consumer regulatory affairs) and whether the technicians are factory-authorized or Automotive Service Excellence (ASE) certified. Such technicians have undergone formal training and passed specific tests establishing their knowledge of your car's various systems. This will decrease the odds of having your car worked on by someone who just keeps pulling parts - and handing you bills. Most shops that employ ASE-certified techs will display the blue ASE symbol and the techs themselves will usually wear their ASE certification on their uniforms. (See for more information about ASE.)

It's also a very good idea to ask current customers of the shop (or dealership) you're thinking about taking your car to about their experiences. Most shops will have a waiting room and usually there are customers inside waiting to pick up their vehicle. You can casually ask them if they're happy with the shop, the work done and so on. If people are unhappy they will usually be quite ready to tell you - and the reverse is just as true.

* Trust (but verify) -

It's not unheard of for a dishonest shop to charge a customer for work they didn't do - or for parts they didn't replace. To guard against this, you can discreetly mark the part - for example, the left front tire if you've taken the car in to have all four tires rotated.

Then, when you pick your car up, you can check to see whether the shop actually did rotate your tires. Similarly, check the dipstick after an oil change to make sure you got what you paid for (fresh oil) and, if you can, mark the oil filter (before you go in for the oil change) so that you can be certain a new one was actually installed.

You may have heard people recommend asking to see the parts that have been replaced as evidence the work was actually done, but it's not hard for a dishonest shop to just pick up an old part from the junk pile our back and present it to you.

The only way to be sure is to mark the part yourself - before it's removed - then check to see whether the part you're shown has that mark on it.

* Don't accept "estimate overages" -

Your final bill should always be within 10 percent of the estimate; never tolerate a final repair bill that's significantly higher than what you were quoted unless you specifically agreed to something after the estimate was written. It's neither ethical nor (usually) legal for a shop to charge you for additional work you didn't specifically authorize.

If you do receive a bill that's significantly more than the original estimate, contest it.

If it's a dealership, ask to speak with the service manager and if that doesn't work, the owner of the store - and from there, complain directly to the affiliated automaker.

If it's an independent shop, try the owner.

If you don't reach an acceptable understanding, head straight for your local town/city's government offices and lodge a complaint with the consumer protection department.

It may take a little time (and hassle) to get it all sorted out - but that's preferable to paying too much, or paying for work you didn't authorize.