By Amy E. Feldman

PHILADELPHIA (CBS) - Donating your old car to charity can be both generous and tax beneficial—if done correctly.

Among the most perplexing ads are the ones that ask you to donate your car to the blind. Don’t worry; you don’t need to stay off the sidewalks.

In case you had the misty-eyed impression that you’re beloved family car was being driven by a person from the charity, most cars donated are sold at auction and it’s the funds raised that are used to benefit the charity.

So the first legal lesson is that you don’t get to deduct the book value of the car, but instead only the amount the car actually garnered at auction, which the charity will let you know. Also, remember that you should look for a charity that accepts your donation directly, avoid the for-profit intermediary organizations that keep the majority of the money.

And, when you donate, don’t leave assignment of ownership spaces on the donation papers blank as some charities will ask you to do, you need to make sure you’re off the title as soon as the car is out of your sight.