How do you prevent corrosion on your car's battery?

You can get a tin of terminal cleaner at your local auto parts store and it will help keep it clean after you have cleaned the terminals with it. Make sure your battery is fully charged.You can also get a paint that can be sprayed on the terminals to help prevent corrosion. If you want to go cheap i would suggest just keeping your motor clean and sand down the rust that gets on the plugs.

Second answer

Clean the terminals with sand paper or a wire brush. Then rub vaseline to the connections and the battery poles. Then reconnect the battery. The vaseline keeps air away from the parts and stops coroision from coming back