Hi Shawna!
We always get a rental car when we vacation at WDW, and I have found that the way to get the best rate is to shop around and check prices often. My first stop when I begin the process of looking for rental car is
www.mousesavers.com . They have a section on their website dedicated to rental cars which includes current promotions and coupon codes for all of the rental agencies located at the Orlando airport.
I usually start looking for a car a couple of month prior to my vacation dates, even though the best deals don't usually come out until you get a little closer to or trip. I will usually reserve the best deal I can find, but I make sure to check all of the agencies again every now and then in case a better deal comes along. If I find a better deal I book it, and cancel my previous reservation.
You can also sign up for e-mails and offers from most of the car rental companies. Every nw and then you will ge special offers sent to your e-mail or you can use your customer number to get free upgrades or avoid waiting in the lines at the counter.
Good luck finding a deal on a car and have fun planning your vacation!