Some things in life are best left to the pros. Snow skiers "hot-dogging" it with multiple flips and twists while zooming down a steep mountainside comes to mind. It isn't only that these things might cause bodily injury. They can also cause damage to property and egos if not done correctly.
Sometimes we lay people are not qualified or fully prepared to undertake certain projects. For instance, jump-starting a car which has a dead battery. How hard could it be? Kmart sells the cables. Hook 'em up and let's go. Hold on. Things can go very wrong. Let me count the ways.
First, if the cables are hooked up backward, negative on one battery to positive on the other, for even less than a second, delicate computer circuits in both vehicles can be destroyed. That is expensive. Secondly, a large arc or spark can be generated when the clamp is hooked up and when pulled off. That spark could take place in a cloud of hydrogen gas that was recently emitted from the battery. Hydrogen gas is what was inflating the Hindenburg Blimp when it went boom. "Oh the humanity," the commentator said. "Oh my singed eyeballs," you may say. I've seen batteries explode in cars. It leaves a bulge in the hood if it's closed. I once had to hold a mechanic down with his head under a faucet to wash the acid from his eyes. He made it okay, but he was a little gun-shy around batteries from then on.
But wait, there's more, like a Ronco commercial. If your battery was dead, there was a reason for it to be dead. If you left your lights on while you went into that restaurant, you know the reason. If that didn't happen, then you don't know the reason. There are at least two other possibilities, and jump-starting it will not fix either of them. Jumper cables never fixed a car, and they can cause new problems.
It might be a bad battery. In that case jump-starting will only take you to another place, where it will fail again, and you might be further from help. It might be a bad alternator, which keeps the battery charged as you drive. If that is the problem, jump-starting will only get you a short distance before the dead battery will kill the engine as you drive down the road. Even if it was the first case, where you left the lights on, jump-starting can cause damage. Since the battery is dead, it needs a lot of charging current to bring it up. After jump-starting, your alternator will sense that dead battery and try to recharge it by generating its' maximum current. That excessive current might turn your alternator to toast. It would be far better to charge up your dead battery before starting the car. If you don't have access to a battery charger, you can hook up another vehicle to your battery with jumper cables, being careful, as I'll explain next, and simply wait five or ten minutes for your battery to charge up before you start it up. Keeping the second vehicle at a slow idle should protect its alternator from harm.
By being careful, I mean to first connect the red cable to the positive terminals on each battery. Look for the plus sign on each battery. If you can't find the plus signs, don't hook up. Get help. After that one is hooked up, connect one end of the black cable to the ground terminal on the battery of either car, and the other end of the black cable to a metal part of the engine on the other car. DO NOT HOOK IT UP TO THE BATTERY POST on the second car. Then if it sparks, which it usually does, it will be away from the explosive battery fumes.
If that's easy to understand, try this one: Tell me why men's bathing suits now touch their calves. Imagine swimming the English Channel dragging all that cloth. Somethings, I don't understand.