WHAT'S THE BEST CAR FUEL ADDITIVE?

I was recently in an automotive supply store, and was a bit overwhelmed by the choices. I live in South FL, so moisture condensation in the gas tank is not an issue. However, I would like to keep the injectors and valves clean, and optimize fuel consumption. What ingredients or additives should I look for? Does anyone have any good or bad issues with a particular brand or type of additives? Any specific recommendation would be appreciated!