Auto-insurance premiums have long since reached big-ticket status, so it pays to look for opportunities that will keep your costs down without sacrificing protection. Here are some things you can do:

Do some homework

Posing as ordinary buyers, investigators with the Pennsylvania Insurance Department once visited 186 insurance agencies in three cities. Of the 92 Philadelphia agents contacted, fewer than 30% volunteered information on discounts and deductibles that could have reduced premiums 20% to 40%.

The lesson: Arm yourself with as much information as you can before you start calling companies. You'll find that some kinds of information are easier to get than others. It is fairly easy to solicit cost, coverage and deductible information from auto insurers; it's much more difficult to find out their financial stability and service record -- things you'd be interested in knowing if, for example, you get a good cost quote from a company you're not familiar with.

You can check out stability in Best's Insurance Reports: Property-Casualty or use A.M. Best 's insurance rating tool on kiplinger.com; insurers with the top two ratings can be considered solid. (You can also ask an agent how A.M. Best, the rating service that publishes the above guide, rates his or her company.)

Also contact your state insurance office; many of them keep track of consumer complaints and will share the results if they're asked. You can also look up consumer complaint ratios on their websites or through the NAIC's consumer resources, at NAIC.org. (Links to state insurance office websites can also be found there.) Finally, read through your policy carefully so that you're sure of the kind and amount of protection you have.

Compare the premiums

Survey after survey confirms that auto-insurance companies often charge greatly different premiums for the same coverage. In New York, Pennsylvania and elsewhere, premiums have been shown to vary sometimes by more than 100%.

Rates may not vary as wildly in your area, but the odds are you will discover substantial differences if you take the time to get premium quotes from a number of companies. Begin by checking out InsuranceRates.com, where you can get quotes from several insurers.Then check out sites for State Farm; Allstate; Progressive; Geico and others. These quotes can act as a measure against which to judge identical coverage rates at different companies. If you'd like individualized help, you can work with an independent insurance agent -- you can find one in your area at IIAB.net

Many state insurance offices distribute auto-insurance pricing guides, but the categories they use may not match yours. Your best bet is to use such a guide to identify your state's most cost-effective insurers. Then get price quotes from a handful and you'll have a truly comparative guide.

Manage your teenagers' driving

Young drivers pay much more than most others because, as a group, they have more accidents. Rates will drop several notches when they reach age 25 or marry. Most companies give good-student or driver-education discounts to young drivers -- commonly 5% to 25% off for a consistent B average -- because statistically, good students are superior drivers. Young drivers can also get discounts for completing an approved driver-training course. The parents of students who spend part of the year at a school more than 100 or 150 miles away from home (and away from the family car) may also get a break.

Drive carefully yourself

Discounts are common for safe-driving records: Some companies give 5% off for drivers with three years of a clear record, raising the discount to 10% for drivers with six or more accident- and violation-free years.

Depending on which company insures you and where you live, you may even get a discount if you're a nonsmoker, a woman who is a household's only driver, a senior citizen, or a member of a certain profession (such as law or medicine) that is statistically less accident-prone.

All ten of the leading insurers polled by the Insurance Information Institute offered a 15% to 20% discount to commuters sharing driving responsibilities in car pools, meaning they don't drive their cars to work every day.

When comparing policies, consider discounts but don't fixate on them. A discount may very well be offset by a higher premium to begin with.

Check your car's rating

Insurers charge more for cars with high claims rates, no matter how good the driving record of the owner. Some charge less for collision and comprehensive coverage on models that score well for safety and durability, but add surcharges for others. A surcharge or a discount isn't a judgment of a car's quality. The rate variations reflect repair costs, accident frequency, theft losses and other factors.

Before you buy your next car, it might pay to check on such differentials. Highway Loss Data Institute and also Car-Safety.org provide loss data on nearly all makes and models,and your agent should be able to tell you the new car's rating.

Loss data do not necessarily translate into discounts, but they do show which vehicles are most likely to qualify.

Consider raising your deductibles

It might make sense to choose the highest deductible you can afford to pay without seriously disrupting your finances. The idea is to pay for affordable damage yourself and let insurance kick in for bigger losses.

Whatever your situation, you can save something by accepting a larger deductible and thus transferring part of the risk from the company to yourself. It's not an ideal solution, but it's one of the few cost-cutting opportunities that are readily available. By raising your collision deductible from $250 or $500 to $1,000, for instance, might allow you to lower your annual premium.However, having a higher deductible prevents you from filing small claims that could jeopardize a claims-free discount.

Reduce the coverage on an old car

You could consider dropping comprehensive and collision coverage on an old car to reduce your insurance costs fast. That would expose you to additional risk, but remember that the insurance company won't pay more to fix a car than it's worth. Each year's depreciation therefore diminishes the maximum claim you can make against your collision coverage.

If your car is five or more years old, depending on its value, you may be better off dropping both collision and comprehensive coverage and banking the savings. Estimate your car's value by checking out the Kelley Blue Book website and consider how much protection you're really buying for your collision and comprehensive premium.

Insure all cars with the same company

You get a break for the second and successive cars covered by the same policy, so it's usually more economical to put all your cars on one policy. Similarly, consider using the same company for other policies. Some insurers offer discounts of up to 10% if you cover both your car and your home with them.

Don't pay by installments

The company tacks an extra amount on to your premium when you pay in monthly or quarterly installments. If you can afford it, pay your premium in a lump sum.

Improve your credit score

Insurers have found a strong correlation between credit history and insurance claims, and in most states your credit score can make a big difference in your auto insurance rates. Make sure you don't have any errors on your credit report that can hurt your credit score; you can get a free copy of your credit report from each of the three bureaus every 12 months at AnnualCreditReport.com. See "Demystifying Your Credit Score for more information about boosting your score.

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