Finding Cheap Car Rentals

This website has a ton of great tips.

You need to understand that each car rental market is different.

More:

2. Compare prices - One of the better sites to check and compare prices is orbitz but if you are travelling overseas consider researching using local sites. If you are unaware of sites in other countries, always check and compare prices from the major car rental agency websites.

3. Think outside the box - If I know I am renting for at least a week, my biggest cost saver is to avoid the airport rentals and their fees. The airport taxes will really burn a hole in your wallet and its a common mistake for renters to see one price on a website and when they return the car, the fees have been added on. Instead, find a location closest to the airport and take a shuttle or taxi to the location. Believe me, its worth it. I recently stayed in Australia for a month and saved of $600 US Dollars by using this method myself. The cost of the taxi was far less than the airport fees and not too much of an inconvenience.