I always use priceline for car rentals. What I do is find a cancellable reservation with codes, etc. that I can live with. Then about a month before my trip, I start bidding. I check hotwire.com with my reservation details to get an idea of what some great rates are, and then start my bid about 1/2 or 2/3 of that rate. You can only bid once every 24 hours unless you are changing parameters. I love priceline! Plus, a lot of the reward sites give you cash back too!