There are lots of great advise and links above. The biggest thing to consider when renting a car is

We will be in the St Pete area for 10 days around Christmas. Does anyone have good ideas or advice on car rentals? I didn't know if anyone had any special sites to look at or if there were some local deals. There are three of us and we don't need a large vehicle. Thanks in advance!
Florida is notoriously high for rentals over the holidays and over spring break etc. Start at rentalcars.com to try and get an idea of the companies san diego apartment rentals that stll have compact cars available. Then, go to Mousesavers.com and cick the link on the top left for "planes and rental car advice", and then click on the link for Hertz or Alamo or whatever company you are considering. Coupon codes and discount offers will pop up with instructions on how to book the deals.
There are lots of great advise and links above. The biggest thing to consider when renting a car is the insurance. In Florida counter staff are known to make six figure san diego apartment rentals salaries (yes, over $100,000/year) selling insurance CDW/LDW. When you are comparing rates and car classes consider if you need to buy coverage. Most people have a credit card that provides CDW/LDW when the car is used to book and pay for the rental. This is provided on most regular credit cards you don't need to upgrade to Gold. Call the number on the back of your credit card and ask their customer svr rep to check and verify that your card provides this coverage. If not, it is worth getting a card that does. Buying CDW/LDW from the rental car company can be as much as $30/day. Debit cards don't provide this coverage