Donating your old vehicle to charity can often allow you to make significant tax deductions, but the process may not be as cut and dried as it seems.

Find out exactly who you are dealing with. If you are speaking to someone from the charity itself, find out if they contract a third party to pick up and/or sell the car. If so, what percentage of the proceeds actually goes to the charity? The charity's cost of hiring these contractors can limit the amount of proceeds that the charity will actually receive.

A good rule of thumb is to donate your car only if the program contributes at least 70 percent of its proceeds to charity. If you're talking to an outside agent, ask what percentage is collected, and then contact the charity to confirm that you've been given the right information.

Get specifics. While there are many legitimate programs out there, there are also a lot of scams. Any legitimate donation program should be willing to provide information regarding the specific charity to which proceeds are actually donated. Therefore, do not donate your vehicle to any organization that says it donates proceeds to "charity" but refuses to specify which charity.

Also, if the charity or intermediary requests that you leave the keys and the title in the unlocked vehicle for it to be picked up, do not do it! There is a significant chance that you will have your car stolen, and, without a valid title, you will have little legal recourse.

Don't take their tax advice as truth. The organization may tell you that you can get a tax deduction for the full Kelley Blue Book value of the car, but in reality it's up to you to determine the size of your deduction.

The IRS allows a tax deduction for donated property based on fair market value. This often represents considerably less than the Blue Book value because it is based on several factors, including condition, mileage, and features.

The charity or intermediary may offer you assistance in determining the fair market value of your vehicle. However, remember that you are solely responsible for how much you deduct—if you're audited, the organization won't be there to help you out. Instead, it is often a good idea to have an auto professional determine the vehicle's fair market value for you.