When you bought your car, you did your homework. Read reviews. Checked reliability ratings and crash-safety findings. Pondered the value of all the gadgets. Compared trunk space and legroom. Test drove it. Avoided dealers' price-negotiating games.

Unfortunately, that other driver — or your own temporary distraction — didn't match your diligence in buying the just-right ride. While even the best body shops can't undo the accident, Twin Cities Consumers' Checkbook's ratings reveal some shops can undo the damage and restore your car to its pre-accident appearance and performance. But those same ratings also reveal that some shops may compound your misery with lousy work and that prices vary widely from shop to shop.

Auto bodywork is difficult to do well. Since any blemish shows on the smooth skin of a car, even ordinary tasks like patching rust spots or blending paint are challenges. Below the surface, precision is equally critical — with an error of less than 1/16 inch in the adjustment of a modern car body frame capable of affecting performance.

In addition to exacting work standards, auto body mechanics also must possess expertise on the properties of metals and plastics; the mechanics of high-tech suspension and steering systems; modern welding methods; the art of paint tinting and blending; and how to spot accident-related damage to mechanical, electrical, air-conditioning, and other systems.

If you, not an insurance company, are paying for the work, shop around for a good price. Checkbook's undercover shoppers called shops to ask for estimates on specific repairs and found drastically different prices, with some shops charging fees that were more than twice as much their competitors' for the exact same jobs.

Don't assume a low price means lousy work. Checkbook found no relationship between price and customer satisfaction. Shops that quoted the lowest prices to Checkbook's undercover shoppers actually scored better on its customer survey questions than shops that quoted high prices.

If an insurance company is paying for the repairs, as is the case with more than 80 percent of auto bodywork, you need a shop that won't let the insurer cut corners. Does the shop provide a clear estimate? Can its representative explain and document the need for each element of the job? If so, chances are good that the shop will get your insurance company to pay for all needed work.

If your car suffers only minor damage, and you are certain there are no structural or other safety-related problems, you probably will be asked to use a drive-in claims center that will provide an authorized repair-cost figure and the names of body shops willing to make the repairs for that amount. Using a drive-in service is convenient and should be satisfactory when there is only cosmetic damage.

Some insurers offer another option: Take your car to a company-designated shop and have the repairs made with no estimate. This can be a big timesaver and an acceptable arrangement if you need only minor repairs.

But if there is even a possibility of serious damage to your car, take it (or have it towed) to a top-rated shop and have the insurer send its estimator there, rather than an insurance company's drive-in appraisal center. The independent body shop will provide a better evaluation of the damage than an insurance company looking to keep down the costs of claims and the best shops will serve as your advocate in dealings with the insurance company.

But for serious repairs, you need a great shop to advocate for quality. Don't count on your insurance company to look out for your interests. Also, bringing your car to a body shop rather than an insurance company's drive-in appraisal center allows the company's adjuster to make a thorough inspection for hidden damage.

If an insurance company is paying for your repair work, make sure that the shop will use OEM (original equipment manufacturer) parts, since there is some concern over the quality of non-OEM parts. Minnesota law bars insurers from requiring shops to use non-OEM parts.

If there's a dispute with the insurer, especially over costs, and your claim is on your own policy, check the policy for an arbitration provision. Arbitration can be time-consuming (meaning you'll probably have to pay repair costs yourself while arbitration proceeds), but it gives you a good chance to get a fair shake.

Check your car thoroughly before taking it home from the shop. Look and feel whether repaired surfaces are smooth and paint has the proper gloss and color. Take a test drive if the damage was substantial. The car should function as it did before the accident.

Ask about guarantees. Most offer a minimum of 30 days' guarantee against defects in parts, materials, and workmanship; some high-quality shops offer guarantees of six months or longer (the length of some guarantees varies by type of job). Whatever guarantee you get, get it in writing.

Twin Cities Consumers' Checkbook magazine and Checkbook.org is a nonprofit organization with a mission to help consumers get the best service and lowest prices. It is supported by consumers and takes no money from the service providers it evaluates. You can access all of Checkbook's ratings of area auto body shops free of charge until April 5 at www.checkbook.org/startribune/autobody.