How do you jump start a car?
1. Make sure both batteries have the same voltage (they probably do unless one car is old). Don’t jump start a frozen battery (it may explode), or a battery with cracks in the casing
Keep metal objects away from the battery. If they cause a spark it could be dangerous.

2. Park the two cars facing each other, close but with enough space to walk in between.

3. Remove the keys from the ignitions, turn off lights/blinkers.

4. Disconnect all accessories (voltage spikes can damage them).

5. Clamp one of the red (positive) clamp to the positive terminal of the dead battery. If there is corrosion on the terminal, clean off or scrape the residue, and/or twist the jaws of the clamp until it cuts through the corrosion and into the metal. Make sure the black clamp of the same end isn’t touching any metal.

6. Connect the other red clamp to the positive terminal of the good battery.

7. Connect the black (negative) clamp to the negative terminal of the good battery.

8. Attach the other black clamp to an unpainted metal surface (e.g. bolt, bracket) on the engine of the car with the dead battery, at least a few inches away from the battery. If a labeled remote negative terminal is available, use it.

9. Confirm that the jumper cables are not near any moving engine parts.

10. Start the booster car, and let it idle for 5 minutes to build up a charge in the dead battery. This will take longer if the dead battery is really empty.

11. Start the car with the dead battery and let the two vehicles idle for a few minutes. If the car doesn’t start, wait a few more minutes and try again. In some instances, slightly revving the engine of the running car while charging the dead battery may help. If it still doesn’t start, it probably won’t.

12. Disconnect the jumper cables reversing the connection order, making sure no disconnected clamps touch any metal or each other

13. Drive the jump-started car for at least 20-30 minutes so it can recharge the battery
Try to keep the jumper cables with you; you may need to jump again the next time you start the car.