Folks, the prices for rental cars will vary based on supply and demand. There is no rule of thumb where you can assume the prices will rise or drop as it gets closer to your reservation date. If you book early and the demand goes up, so will the prices. If you book early and the demand goes down, so will the prices. I've gotten great prices 3 months ahead of time and 1 day ahead of time. It all depends. Like other posters have stated, book early and keep checking back often. Rebook if you find a cheaper price. Most rental companies do not charge for a reservation or cancellation. In addition, place a Priceline bid the day before your reservation for a total amount at about 20% less than your existing reservation. If you get it, great. If not, you still have your original reservation. Be aware that Priceline will not allow you to name your own price for one-way rentals (i.e you are returning the car to a different location).