To jump-start a car with a dead battery, you'll need jumper cables and either another car with a working battery or a portable jump starter. Ensure both vehicles are parked safely, turned off, and not touching. Connect the jumper cables or jump starter to the batteries, starting with the positive (red) and then the negative (black) terminals. Once connected, start the working vehicle, then attempt to start the dead vehicle. After the dead vehicle starts, remove the cables in reverse order.