When you go on vacation, or need a car for a business trip, it is always best to reserve a car prior to getting there.  Often in prime locations, (such as Hawaii), if you don't have a car reserved in advance, you will find there are no rental cars available.  Also, you will pay a premium price if you wait until you get there.  I have found the best way to rent a car is through Priceline in the name your own price field.  The first time you bid a price, make it a lot less than you really want to pay in a class less than the one you want, then when it is rejected, bid the price you really want, (within reason).  You will need to  raise the rental date or class of car to do this.  Most of the time I have obtained the car at the price I wanted, such as an economy car in Hawaii for $11 per day, which is about $10 to $20 per day less than normal.  You want to check out Expedia, Travelocity, etc for ballpark prices first, then get your price at Priceline.  Sometimes you won't get a deal at Priceline, then you take the next best price you found earlier.  Either way you will have your car waiting for you when you get there.  Also, make sure if you have a reward for airlines miles, ask the rental agency if they're a partner so you can get credit.

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