(MONEY Magazine) – Even though I write about cars for a living, I'd never buy a new one without test-driving it first. Yet many people do--and it's a big mistake. It's essential to get behind the wheel for a tryout. That's the only way to truly evaluate a vehicle and determine whether it's right for your needs.

Plenty of shoppers skip this step and regret it. "We get lots of calls from people who want to get out of their lease or trade in a car they bought not long ago," says Ashly Knapp, president of car buying service AutoAdvisor. "In almost every case, they didn't test-drive the car."

A smart test drive means more than just taking a quick spin. Below, I'll show you how to make the most of the drive.

First, though, here's some general advice. Most car salespeople would prefer to be in the showroom making deals rather than on the road with you. To ensure that you get the time you need and the car you want to drive, make an appointment. Once you do, plan out a route that allows you to experience the car for 20 to 30 minutes in the driving conditions you face most often. If you do a lot of highway driving, make sure you plan for that in your test. But don't forget to try the vehicle in a variety of conditions--on rough road or in bumper-to-bumper traffic. And remember that most of what you're judging is subjective; whether you like the car often comes down to personal taste. Remember too that a test drive may reflect on the dealer's service, as I learned when I recently visited Toyota and Chevrolet dealers anonymously. At Toyota, my Camry test went off without a hitch. At Chevrolet, things were a mess. They didn't have the 2002 TrailBlazer SUV that I'd reserved and asked me to drive the 2001 Blazer instead. Now, on to my guide to test drives, which I've organized into eight separate mini-tests.

The visual test. The best way to start your test drive isn't by driving at all. It's by making a detailed visual inspection of the vehicle from an inside-the-car driver's point of view. Once you've adjusted the driver's seat so that you're comfortable, examine the radio, clock and climate controls. You want to be able to quickly glance down at these without having to take your eyes off the road for more than a second. Many auto manufacturers don't make that so easy. The radio and clock in my Ford Explorer, for instance, are set so low in the console that I have to bring my head down to see them.

Similarly, check the view through the windshield. I prefer cars like the Honda Accord and the Ford Escape, which have low, lean dashboards that give you a wide- open view of the road. Cars with wider dashboards can obscure that.

The comfort test. After you've taken in the visuals, hit the road and judge how the car feels. Start with the creature comforts. Ask yourself whether you feel secure in the seats and can safely command the car from behind the wheel. When I test-drove the 2001 Blazer, I noticed the seats were tipped backward too much for my taste and that there was no control to adjust the angle.

Try adjusting the seats using the power controls while driving. You shouldn't have to stop the car or even look away from the road to change your position. Then check whether all the controls--for the power windows, stereo, heater and A/C--are easy to reach. They too should be easy to use while driving.

Next, evaluate the visibility from the rearview and side mirrors. Every car has a small blind spot or two, but be wary if a large vehicle is out of your sight for several seconds on one side or the other (a problem I noticed when I recently drove the Pontiac Aztek).

The power test. Now it's time to test the car's performance. Floor the gas pedal while merging onto the highway. If the car can't flow easily into traffic, you may want to consider a car with a bigger engine. (When I test-drove the four-cylinder Toyota RAV-4, for example, I found it too sluggish in these situations.)

The brake test. If you are near a shopping mall with a quiet parking lot, pull in, speed up to about 45 mph, then slam on the brakes. The car should stop within 100 feet. This test allows you to see how smooth and efficient the brakes are. Failing a handy parking lot, slam on the brakes as you approach a stop sign. The pedal should feel firm, not mushy.

The suspension test. Not every car handles bumps the same way, so drive over railroad tracks or on less than pristine roads. If the car feels bouncy or jarring, you probably won't like driving it long term.

The ear test. Lend an ear to what the car sounds like, in three different ways. First, with the radio off and the windows closed, ask yourself whether you find the noise level high, low or medium. As a yardstick, use the sound level in the car you currently drive or test-drive several models in the same class of cars. I consider the sound level high if I have to play the radio to drown out road or wind noise, and low if my driving companion can hear me whispering. Second, turn on the heater full blast followed by the air conditioner. Some cars blast so loudly, they're a nuisance. Also, turn on the radio and judge how it sounds against those in other cars you've driven. Third, ask the salesperson if the radio is standard or optional. Depending on the answer, you may want to upgrade.

The in-and-out test. Once you've finished driving, get in and out of the car a few times to see how easy that is for you. I've found that big sport utilities, like the Ford Expedition, are difficult to get into unless they have running boards below the doors. While you're at it, hop into the back seat to check headroom and legroom. When I drove the Mercedes C320 re-cently, it was roomy up front but a real squeeze in the back--a big surprise. Also check the trunk. You can read about a trunk's cubic capacity, but there's nothing like seeing it yourself.

The heart test. Finally, choosing a car is more than just a practical matter. It's about how you feel in your gut. So ask yourself: Is this a car I absolutely love driving? With all the money a new car costs--and all the different models available--the answer should be yes.

Senior writer Jerry Edgerton is the author of Car Shopping Made Easy. He can be reached at car_guy@moneymail.com.