How to Properly Clean a Car's Battery

I suggest you to get a battery cleaner kit that comes with the two sprays and the circular metal brush.
You can get the other metal brushes from Harbor Freight.
A good battery contact is key for everything working correctly on your car.
You would be surprise how many issues arise from having a poor battery or a poor connection. If you see the blue stuff around the battery connections then it is time to clean (you are actually passed that point ;-)