If you've ever turned your ignition key and absolutely nothing happens, then you might have a dead battery. (Note: make sure you always have jumper cables in your car) Make sure both of the cars are turned off. Connect the red (positive) cable to the positive (+) connector of the dead battery. Now connect the other end of the red cable to the positive connector of the good battery. The red cable is set up and good to go. Now for the other cable. Connect the end of the black (negative) cable to the negative (-) connector of the good battery, and take the other end of the black cable and connect it to a bare, unpainted metal surface of the stalled car. A good area to connect it to is the engine block. Start the car that has the good battery and keep it running for about 3 minutes. After 3 minutes, start the dead car up, and remove the cables in reverse order. Keep the car that had a dead battery running for 30 minutes to allow the battery to charge up.
After the 30 minutes pass, close the hood and enjoy your working car!