1. Do an online search for the phone number.

Pay-as-you-go mobile phones and call-forwarding services give curbstoners phone numbers that are disposable and hard to trace. However, a quick Internet search for the phone number listed on a car or classified ad will reveal whether that phone number has been used recently in the sale of other vehicles. If it has - beware!

2. Snoop around.

Because curbstoners usually have several vehicles to sell, many use special software to quickly post several online classified ads at once. As a result, their listings may appear close together if you view all the ads chronologically.

So, it might be worth your time to call the phone numbers in the listings above and below the one you actually want. If the same person answers, even though the phone numbers are different - you're probably talking to a curbstoner!

3. Don't reveal too much at first.​

When you call, one smart gambit is to say, "I'm calling about the car."

If the seller replies, "Which car?" - then you have to ask yourself how many private parties have more than one car for sale.

Yes, people get deployed, families get relocated, and car buffs downsize their 

collections - all reasons someone may be selling two or three vehicles at once. But if it seems like a person is selling several popular automotive models and nothing else, that's a warning flag.

If you're talking to the owner, ask how long he or she has owned the vehicle.

Answers like "I'm selling it for a friend," or "It's my grandmother's car," or "I've had it a couple months" are warning flags. At a minimum, it means the seller may not know much about the car's history. At worst, the seller may be flipping salvaged cars for profit - curbstoning.

5. Check the address.

Although many genuine private sellers are reluctant to meet at their homes for legitimate safety reasons, the vehicle owner's address will be on the registration and title. Don't hand over your money until you've confirmed that the addresses on the registration and title are, in fact, the seller's address.

If the purchase requires a significant amount of money, you might even want to drive by the address listed to make sure it's real, and to form a better sense of how the vehicle was cared for.

6. Ask to see the vehicle's maintenance records.

Because curbstoners are all about flipping used cars for profit, they seldom have the maintenance records for the vehicles they sell.

If the seller doesn't have the maintenance records, then ask where the work was done. Contact that repair facility and ask to see the maintenance and repair records.

While you're checking the records, don't overlook the obvious: make sure the name shown as the vehicle's owner matches the person you're dealing with.

If the current owner has had the vehicle for only a short time, or lacks information about the repair history, try contacting the previous owner.

Don't just give the car a road test; most cars can be made to work fine for a ten-minute drive. Try getting on the freeway, passing, and stopping. Find a parking lot and drive carefully in a circle to the left and right to reveal steering issues. Speed bumps are great tools for revealing worn (and costly) suspension components.

Make sure all the systems work, including the air conditioning and heater.

Finally, check all the electronics and accessories: the CD player, all the power windows, and the central locking system.

Having a second set of eyes along can prove helpful in checking turn signals, brake lights, and whether the car tracks and stops in a level, straight line.

8. Have the car inspected.

Most mechanics will look over a car for a nominal fee, usually less than 

$100.

Although a CARFAX report is great, it only looks at what's documented.

For instance, it might show that damage from a minor fender-bender had been repaired, but it can't possibly examine how well that repair was done. And, conversely, work that the owner did personally may not show up as part of the vehicle records.

This gap between documentation and reality becomes bigger when looking at high-mileage vehicles, older vehicles, restored or customized vehicles, and collectibles.

Also, it should be noted that a false VIN would produce a false report: one that belongs to the VIN plate, but not the rest of the car.