1. Choose the Right Shop
Consumers have three basic choices when it comes to taking a car in for repair. You can go to the dealer, find a department or chain-store franchise like Sears or Meineke, or try an independent mechanic at a service station. Where you should go depends on what type of repair you need. But watch out: Mechanics in each type of repair shop will try to convince you that they are the best ones for the job.

Dealers — Clearly, any work under warranty should go straight to the dealer. That's where you'll find some of the best-trained mechanics for complicated jobs such as electric, chassis, fuel injection and engine work. But if your car isn't under warranty and you're paying for the repairs, you should think twice about having your dealer do the repair. Why? Dealers charge more, perhaps $5 to $10 an hour more for labor and a steep premium for factory parts at a dealership.

Chains — Most routine repairs and services — brakes, tires, batteries, mufflers and oil changes — don't demand highly paid mechanics. If you don't have a mechanic you rely on, think of these as commodities, and go shopping for a good price at a convenient location. With mufflers, for instance, it's nearly impossible for dealers or independents to compete with chains. In suburban Detroit, Roy O'Brien Ford charges about $245 for a new muffler and exhaust system. Midas does it for $105. Be sure, however, to go to a chain that specializes in the repair you need. You probably don't want a brake-shop mechanic fiddling with your transmission, no matter how much he assures you that he can do the job.

Independents — A mechanic you trust is worth his weight in gold. So if you find an independent you're happy with, start there for routine stuff. Even if he charges a little more, the peace of mind is probably worth it. But beware: Independent mechanics may or may not know how to do more complicated repairs. Automobiles have become incredibly sophisticated in the past 10 years.

Most mechanics haven't. Jim Steiger, special projects director of the American Automobile Manufacturing Association, says the industry has a "big shortfall" of properly trained mechanics in the computerized systems found in most cars today. This has been especially tough on service stations. Their share of the auto-repair market has slipped to about 24%, from close to 40% a decade ago, according to Hunter Publishing, a Des Plaines, Ill., trade magazine company. And it's a vicious circle: Less volume at independents means less money to pay for the expensive diagnostic equipment they need to spot major problems.

Dealers, on the other hand, are required by most manufacturers to buy such equipment. And their technicians are more likely to be trained in these complicated repairs. If you don't drive an American car, check out the so-called specialty shops that focus on only one or two foreign makes. Mechanics at these outfits are often as well or better trained than those at the dealer and they usually charge less.

2. Beware Unnecessary Repairs
Back in 1979 the Department of Transportation found that 53% of the costs associated with auto repair were unnecessary. At the time, that translated into a $26.5 billion loss to consumers. Unfortunately, things haven't gotten much better since. Consumer activist Ralph Nader estimates that because the industry has grown so much, the total loss has jumped to $40 billion.

The worst of these phantom repairs is the result of outright fraud. Some scam-artist mechanics, for instance, have been known to plunk a seltzer tablet into a battery cell, causing it to boil over.

Or they may squirt oil on your shock absorber to make you think the seal is broken. Then there are the simple, everyday affronts such as the gas station attendant who doesn't push the dipstick all the way down when checking the oil, prompting you to buy an extra quart.

Being paid on commission is often at the heart of a repairman's overzealousness. This is what got Sears into so much trouble, when California accused the department-store chain of selling unnecessary auto repairs and service. Sears has changed its compensation system, but some other department stores have not followed suit, says Chris H. Stevenson, a former mechanic and author of Auto Repair Shams and Scams: How To Avoid Getting Ripped Off. Mechanics who work in franchised shops are often under strict quotas to sell a certain amount of tuneups, oil changes and other services per day or week, Stevenson adds.

Most often, however, "unnecessary repairs are really a matter of incompetence," says Jack Gillis, author of The Car Repair Book and director of public affairs for the Consumer Federation of America. When a repair baffles a mediocre mechanic, he or she will probably keep replacing suspect parts until the problem finally is solved. Many of the parts replaced have nothing to do with the problem, but you may wind up paying for them anyway.

A good way to avoid this problem is to ask to see any old parts. Some states even require mechanics to give you any parts they have removed from your car unless the warranty requires they be sent back to the manufacturer. In addition, Gillis suggests taping to your steering wheel an itemized list of all the repairs you want made. That way the mechanic who works on it — in most cases not the person you talked to when you drove in — will have some instructions from you.

3. Check Your Mechanic's Certification
The National Institute for Automotive Service Excellence certifies mechanics in eight specialties, including brakes, electrical systems, engines, and heating and air conditioning. Although auto mechanics must have two years of experience and pass an extensive standardized exam to become certified, an ASE sticker in your repair shop's window is no guarantee that the work will be done well.

Most repair shops hire both certified and uncertified mechanics. And only 20% of ASE mechanics are certified in all eight specialties. That means that when you bring your car in to fix an oil leak, a mechanic certified in air conditioning may be doing the work. He's certified all right, but not in what you need. Be sure to ask who is going to do the work on your car and what areas that person is certified in. You might also check to see when the certification expires. Mechanics are supposed to go in for a refresher course every five years, but the ASE can't make them take down their stickers if they fail to do so.

In addition, look for repair shops that are endorsed by the American Automobile Association. These facilities must meet rigorous standards and guarantee their work for AAA members. Also, AAA will arbitrate any disputes between its members and approved shops.

4. Get a Second Opinion
Since most shops have a vested interest in making sure you get as many repairs in their bays as possible, it's difficult to fully trust even a trustworthy mechanic. One solution to this problem might be to pay $30 or $40 to have your car checked at a diagnostic center that is not affiliated with a repair shop. A good bet would be one of the shops operated by the AAA. They have no reason to recommend unnecessary repairs. And you'll be armed with important information about your car's condition before you start negotiating with mechanics.

5. Take Your Mechanic to Task
To avoid problems with a new mechanic before the work starts, you might consider checking to see if there have been any complaints logged against the shop with the Better Business Bureau. Check also with your state's department of consumer affairs, the motor vehicles department, the district attorney's office or the attorneys general. This is a hassle, no doubt about it, but assuming you want to develop a long-term relationship with your mechanic, it might be worth the investment of time.

If you feel you've been wronged by the mechanic, you can certainly take action. First, be sure to file a complaint with the Better Business Bureau and the attorney general's office so other consumers who check might benefit from your bad luck. Then, depending on the state you live in, you can get even more aggressive. In California, for instance, the Bureau of Automotive Repair mediates or investigates each complaint it receives. To check if your state has a similar agency, contact your state highway department. Finally, if your garage is endorsed by the AAA, be sure to contact the organization. If your complaint is egregious enough, or joined by others, the garage may lose the AAA's seal of approval.