There's a saying in car repair shops, that: "If it's stuck, don't force it, get a bigger hammer." Naturally we're kidding. Most of the time.
Sometimes things stick big time and the only recourse is to beat the snot out of it to get it loose. A few blows with a big hammer is quicker than a dozen taps with a smaller one, and a lot more satisfying to the frustrated wielder of said hammer. Provided, that is, something didn't slip during that blow and cause a crushed knuckle. There are, however, some things that might respond to a smaller hammer, and some of these tricks might be useful to non-mechanics.
Sometimes a starter motor will suddenly fail to operate. You turn the key and there is only a faint click, but no RRRRRRRR of the engine turning over. To distinguish whether the problem is the battery or the starter, turn on the headlights. Have someone watch them as you turn the key. If the lights go out when you turn the key, it's probably a battery problem. If they stay bright, your problem is probably the starter. The problem is usually poor contact of the brushes in the starter, because they're worn out. In many cases, a small jolt delivered to the case of the starter with a hammer will jostle them into a better contact and the starter will work. If you do this, don't turn it off till you get to a repair place, because it may not work twice. You have a worn out starter that needs to be replaced. Don't listen to anyone who tells you that you only need a solenoid. Starters and solenoids should come as one piece. Of course, you have to know how to recognize a starter when you see one, and they are often located in really difficult places. In the Cadillac Northstar engines, they're under the intake manifold, so don't even think about it. If you're not sure, don't hit it. Hammer blows to the wrong part of the engine could cause more trouble than you already have.
Power windows are a common failure in most cars. It is either a bad switch, or a bad motor, or a broken regulator, which is the mechanism that holds the window glass and is driven up or down by the motor. All the windows usually share one fuse, but each window has it's own motor and regulator and switch, and there will be a master switch at the driver's position. If you hear a motor running when you push the switch, you're problem is the regulator. If you don't hear a motor running, it's either a bad motor or bad switch. Some disassembly is required to check voltages to diagnose it.
There is a trick, however, that may get your window up if it's stuck down in a rainstorm. If the problem is the motor, it may respond the same way a starter motor would. In this case use the heel of your fist and strike the inside door panel about in the middle. Pick a place that won't hurt your hand. If the window works, don't lower it again. You've used up all your good luck for this project.
Fuel pumps are all now located inside the gas tanks, and they are electric motor driven pumps. They fail, usually without warning. You get in the car in the parking lot of the grocery store and it just cranks and cranks. No start. It may be physically difficult to do, but sometimes a blow delivered to the bottom of the fuel tank, about as hard as a moderate kick, will jostle the pump motor enough to get it started one more time. It probably won't work twice, so drive to a repair shop before you shut it off.
We hope none of these things happen to you, of course, but if they do, these tricks may get you to some help, and if they work, they aid in the diagnosis also.