If your car is not starting and you are not sure why. The best place to check first would be your car battery. More often than not the car battery dies down in the most inconvenient of times. So make sure to always keep a set of jumper cables in your car. Now onto the DIY.
Step 1: Connect the two red positive ends of the jumper cable to the red postive good and bad batteries of both cars. As shown in the 2nd picture. DO NOT CONNECT THE RED TO THE BLACK. Only connect the wires to the matching colors or it may destroy your battery.
Step 2: Connect the black negative cable to the black negative terminal on the battery of the good car.
Step 3: Connect the black negative cable to a non-painted metal section of the car. Look for something that it shiny. Most likely these pieces are near the engine. You may see a spark which will indicate a good ground. Don't worry you will be safe!!
Step 4: Turn on the the good car
Step 5: Turn on the bad car after waiting a couple of minutes. If the car starts take off the cables in the reverse order that you put them on and let the car run for a few minutes so that the battery can recharge.
**If the car battery dies again after you start the car then you may have alternator issues**