There's nothing like that new-car smell. Buying a new car has a lot of allure: It's brand new and it's all yours; nobody has abused it. You can get the vehicle equipped just the way you want, and you get the full factory warranty. But hold on. Your best deal could well be a late-model used car.

The used-car market has changed dramatically in the past few years. To start with, today's new cars -- and thus used cars -- are simply made better. Overall quality and durability has increased as U.S. manufacturers pushed hard to catch up to imports. A second factor is the rise of leasing. About one-third of all new cars now are leased -- up from 20% as recently as the early 1990s. Nowadays, the torrent of well-kept two- and three-year-old cars returning from leases is providing a supply of attractive, reliable used cars. And new used-car superstore chains are making it easier than ever to buy with huge inventories and no-dicker shopping. The kicker is that if you opt for a three-year-old model instead, you could save as much as 30% to 40% over new.

In response to the competition from superstores like CarMax and AutoNation USA, car dealers, backed by manufacturers, have introduced what they call "certified" used-car programs for newer used cars (usually up to three years old). Manufacturers insist that a used car must pass a series of inspections before it can become certified. And once a car passes, the manufacturer adds a fresh warranty of 12 months or more.

If you want a used car, start by checking prices of the vehicles that interest you. Among the best Websites are Edmunds.com, run by Edmund's, the publisher of paperback guides to automotive prices, and Carpoint.msn.com, Microsoft's automotive site. Both are free, and both will let you check the going prices for almost every make, model and year you can imagine. (The sites list new-car prices as well.)

These sites also offer classified ads for used cars, mostly from dealers. Enter your Zip code and you'll get a selection of cars within 100 miles or so of your home. While ads for these same vehicles undoubtedly also are running in your local paper, you get more detail on the net. Additional used-car classifieds are available at Cars.com.

Once you zero in on some possibilities, you need to double-check them. Unless you are buying a certified used vehicle, or a car that's still under the original warranty, spend a little extra to check any specific car, truck or van you are close to buying. The first step lets you make sure the odometer is honest and that the car has never been totaled (the used-car business may have become less sleazy than it used to be, but problems still do occur). For $14.95 per vehicle on the Internet (Carfax.com) or $29.50 by fax (800-274-2277), the database firm Carfax will track down the history of your prospective vehicle by its Vehicle Identification Number (VIN), usually listed on a metal plate just inside the windshield. If, for instance, the car had 50,000 miles when its title last changed but now shows 30,000 miles, take a pass. If the car has ever been sent to a junkyard, a salvage title will show up on the report. About one in nine cars in its database has some kind of problem, say Carfax officials.

Once a car has passed those big hurdles, you still need to get it checked by your own mechanic, if you have one. If you don't, many cities have specialized mechanic services that will make on-the-spot inspection of used cars for about $119. One such franchised inspection firm, CarCheckers of America, is in eight locations including Atlanta and Denver. If you are considering spending $15,000 for a used car, that $100 to double-check it may be well spent.

The most important thing to remember: Anything's negotiable except the right to inspect. If the seller won't let you and your mechanic inspect the car, walk away, no matter how nicely it runs.

Often, this rule of thumb means you'll be buying from an individual rather than a dealer, for many dealers don't allow inspections. Those who do typically won't let you take the car off the premises and won't let you use their lift.

Unless you have an unusually close relationship with your mechanic, he'll want you to bring the car to his shop. This isn't unreasonable, for a lift is essential for hunting nasties like rust, worn brake drums and deteriorating exhaust systems. However, a good mechanic can tell a lot from sliding underneath the car, inspecting the exterior paint for repaired body damage and checking the odometer reading against actual wear.

Confining your search to individuals usually means you'll get a lower price -- but it's more time-consuming, because there's only one car at each location. Regardless of where you buy, there are some rules you can follow.

Jack Gillis, director of public affairs for the Consumer Federation of America, recommends what he calls the "touch and comment" technique often used by new-car dealers when they inspect trade-ins. "When you review the car, visibly point out the various problems that you note," he says. "An exaggerated touch of some loose parts or running your hand along body damage can put the seller in a defensive position."

This tactic can be used effectively when your mechanic is conducting an inspection within an earshot of the seller. Have your mechanic mention each problem, allowing you to comment grimly.

Having your expert on hand can make all the difference, because even if you know a lot about cars, you need an expert witness to present the damning evidence. Like any expert witness, however, mechanics must be paid. Some shops offer a pre-purchase checkout for a set amount that can vary widely depending on the shop and the procedures performed. Others offer on-premises inspections for their hourly labor rate, which can range from $40 to $70 an hour, depending on the region and the type of shop.

While indispensable, your mechanic is your consultant, not your agent. To get the best possible deal on a used car, you must do some work yourself. Some pointers: