If you’re unsure how to jump start a car, look no further. Here’s a rundown of what you need to do.

It happens to most drivers at some point—you go to start up your car and the battery is dead. If you’re lucky, you can wave down a good Samaritan or call a friend, but either way, it’s important to know how to jump start a car yourself.

Test Battery

Does your engine crank slowly when the key is in the “on” position, or do all the accessories remain off? If the answer to either of these is yes, you might have a battery issue, according to the Chicago Tribune. In this case, you’re going to need help from a friend with another vehicle.

Be Prepared

Carry cables that are in good shape. This means there should be no exposed wire, a well-insulated gauge, and clean clamps. According to Meineke, the proper gauge varies, so make sure you have the right size. A shorter cable will transfer a charge faster, but it needs to be long enough to span one engine to another with plenty of space in between when you jump start a car. Also, carry goggles and a pair of plastic gloves to keep any acid off your skin and your eyes safe in case of an explosion.

Follow Instructions

Always check in with your owner’s manual. Most cars use the described method of jump-starting, but a few differ. Park the cars facing each other but not touching. Put both in park—or neutral for manual transmissions—and set both parking brakes. Turn off the engines and all accessories, and unplug any electronics. Open both hoods and check batteries for any cracks or leaks. If there are signs of battery damage, don’t proceed until the battery has been replaced.

Identify Terminals

The positive lug is generally bigger, has a red cable attached, and a plus sign stamped on it, says YourMechanic. The ground terminal is smaller, has a black cable, and a minus sign. It’s important you don’t confuse the two. Unravel your jumper cable on the ground and note that each end has a corresponding red and black clamp.

Sequence Matters

Connect the one red clamp to the red terminal of the working battery. Make sure none of the other clamps touch each other or any part of the car besides what’s intended. Next, connect the black clamp to the negative terminal on the good battery. Head over to the other car, keeping two remaining clamps separated. Connect red to the positive, but instead of putting the black end on the negative terminal, clamp it to a solid, unpainted, unmoving metal part of the vehicle at a distance from the battery. This will help avoid sparking that could potentially ignite invisible vapors hovering on the surface of the battery, causing an explosion. Always follow proper safety procedures and never lean over the batteries at any time. Additionally, don’t smoke nearby.

Charge It Up

Turn on the good car and run for 1–2 minutes. Try starting the other. If the engine won’t turn over, check all the connections to ensure good contacts, and run the first car another 5 minutes, revving the engine a little. Try to start it again. If you’ve still got nothing, it’s time to call in a professional.

Drive Away

If it does work, don’t turn off your car. Disconnect the cables in the opposite sequence. Start with the black from the jumped car’s metal surface, positive terminal on the bad battery, negative terminal on the good battery, and lastly disconnect from the positive terminal on the good battery. Take the car for a drive for more than 20 minutes, giving the alternator time to recharge the battery on its own.

Just in case, don’t shut off the engine until you’re in a place that’s safe and convenient. As Popular Mechanics points out, remember you might have a battery drain. And until that’s fixed, you’re may need many good Samaritans to get you out of a jam.

Blair Lampe

About the AuthorBlair Lampe

Blair Lampe is a New York-based freelance writer and mechanic.  She travels frequently and on a budget, which she documents on her website TheGreyBeyond.