1. Get a working vehicle. Bring it to the disabled vehicle.
2. Verify that both the dead battery and the rescue battery have the "same" voltage. Car batteries are usually twelve Volts. Trucks/tractors may operate on a twenty-four volt system, sometimes two twelve volt batteries combined to make a twenty-four volt system. Do not attach 12V to 24V.
3. Position the vehicles so that the car batteries are close enough to each other for your jumper cables to reach each one. Make sure the cars are not touching.
4. Turn off both engines. Open the hood of each of the cars.
5. Turn off the headlights, wipers, radios, and all accessories on both cars. Unplug anything charging in the cigarette lighter. They waste power and might even be damaged by surges of power.
6. Don't attach neg. to pos. Do not attach in series. That may damage electronics.Untangle and unwind the jumper cables. The jaws of the cable clamps are designed to bite into the soft metal of the battery clamps that are attached to the battery terminal posts. Don't attach neg. to pos. so do not attach in "series." That may damage the electronics.
7. Use safety: if goggles or gloves are available, put them on now. Have anyone not wearing safety equipment stand clear of both vehicles.
8. Visually check both batteries for cracks, leaks, and damage. If any of these exist, STOP. Call a tow truck, do not attempt to jump the car, do not even connect the cables.
9. Connect a red clamp "first" to the (+) positive post on the dead battery. Then connect the other end with the red clamp to the (+) positive post on the good battery.
10. Connect a black clamp to the (-) negative post of the good battery.
11. Connect the only remaining clamp (a black clamp for the dead battery) to a solid piece of grounded metal (best if it is clean and non-painted) on the dead car. Avoid connecting this clamp to the negative post of the dead battery--do this only as a last resort. (See tips for suggestions on what to clamp to)
12. Start the working vehicle so it can be charging its own battery and the dead one.
13. Let it idle for approx. 5 minutes before trying to start the other car. Never race the engine. If a "fast" idle is not enough to charge the dead battery then it's not going to charge.
14. Try to start the disabled vehicle. If it doesn't start, wait another five minutes for a little more charging, and try again. Repeat until the disabled vehicle starts.
15. Remove the jumper cables from the vehicles in the reverse order from when you attached them (so remove one clamp from the ground of the recently disabled vehicle, etc.).
16. Keep the recently disabled vehicle's engine running a little above idle for at least at least twenty minutes to charge the battery.