Disconnecting a car battery is a useful skill! First, make sure the vehicle is turned off and you're wearing safety gloves. You'll usually need a wrench to loosen the negative cable's clamp (black), and always disconnect it first to avoid any short circuits. Next, move on to the positive cable (red). What makes you want to disconnect the battery? Are you working on a repair or perhaps storing the car? I'm here to help if you have any more questions!