There's typically a 10-20 percent difference between what a dealer will give you for your used car or truck as a trade-in -- and what you could probably sell a used car for yourself.

The downside, of course, is that you have to sell your used car yourself. And that means dealing with off-hour phone calls, interacting with strangers -- some of whom may be sketchier than the people you sometimes see on Jerry Springer -- as well as the attendant paperwork hassles.

But the process of selling your used car will go easier -- and you'll be happier at the end of it all -- if you adhere to a few basic rules:

*Don't drive around with a "used car for sale" sign (and your home phone number) taped to the car -- This can encourage crimes of opportunity, i.e., no-good-niks spot you (especially if you are a woman) in the car and target you. Place a used car for sale ad in the classified section of your local newspaper or on Autotrader.com instead; this way, you can screen people over the phone; if someone sounds weird or gives you the creeps, you can always just tell them the car has been sold.

*Only agree to meet with prospective buyers someplace safe and public -- Your work, for example. For the same reasons mentioned above, try to avoid having strangers come to your home. You should also specify in your ad acceptable times to call -- and times after which you do not wish to be called.

* Describe the car objectively -- revealing known flaws (if any) as well as providing relevant documents such as service work invoices, etc. If you are trying to sell a used car that has a bad transmission of needs brakes -- inform prospective buyers. Playing fair is not only the right thing to do -- it pretty much eliminates any worry about an irate "sucker" tracking you down later to get even. If you are selling a used car that has any defect or problem that could make it hazardous to operate, do not allow unsuspecting people to operate the vehicle. You should have any such problems fixed before you put the "used car for sale" ad in the paper -- or indicate in the ad that the vehicle is not currently in operable condition.

* Ask to see a driver's license and proof of insurance before you let a buyer drive the car -- and make absolutely sure the driver is at least 18 years old. Never, ever allow an unattended minor to drive your vehicle; if they wreck or damage it, the under-18 driver may not be legally responsible. Insist a parent be present before allowing a test drive. Also be aware that if the driver is uninsured, you could get left holding the bag in the event an accident happens during the test drive. Be sure to write down the prospective buyer's DL info -- and make sure the person matches the description before turning over the keys.

*Don't sign or turn over the title and keys until you've got payment in full in cash or its equivalent; no personal checks. Draw up a simple bill of sale stating the make/model/year of the used car, the mileage, sellers and buyer's names, the sale price -- and that the vehicle is sold "as is." This last part is important to protect you in case the buyer later claims the used car had some unknown problem or subsequently broke down -- and wants his money back.

* Be sure to remove your license plate(s) from the vehicle before the buyer drives away. If you don't and the buyer leaves the plates on, you could be liable for traffic tickets, etc. that are tied into the plate number -- and to you. Immediately notify the Department of Motor Vehicles (and your insurance carrier) that the vehicle has been sold; this way, you want to be charged for registration fees/property taxes and/or insurance premiums that no longer apply. You may even be eligible for a pro rata discount if you prepaid any of these fees for the full calendar year.

Finally, you may want to consider a consignment lot to avoid all the hassles of selling a used car yourself. For a fee (either a flat fee or a percentage of the sale price) the consignment lot will sell a used car for you: put the car on its lot, show it to prospective buyers and handle all aspects of the transaction - including the paperwork/title transfer. You give them the car -- and pick up a check when it's sold. (Many new and used car dealers will sell a used car on this basis.) For a lot of people, the fee involved is well worth avoiding 11 p.m. phone calls from weirdo buyers, having to deal with "tire kickers" -- the lost Saturdays waiting for some guy to show up to look at the car, etc.

You could also just trade it in -- and let the dealer deal with all this stuff!