Newer houses, if you look behind the outlet you will going to have a box, and in most cases it will be a blue plastic box. If you have a little bit of an older house, you may have a metal box behind the outlet. There are different ways to check if the electricity is on or off, you could use a meter, but the best way to go is with a non-contact voltage detector, these checks for electricity in the cable and in the outlet itself and you could pick it up at your local store fairly inexpensively. Just press the switch on and it beeps if there is electricity.
Your breaker box has a main breaker on top, and then you have the sub breakers which control various different circuits, depending on the initial layout of the switchboard manufacturers. So at the very least http://www.eiprojectsolutions.com.au/control-panels/ you have to make sure that the circuit you`re working on is closed, you can do that by just flipping the breaker off, or if you can`t find it or it`s just too complicated you can always just turn on the main and that will turn everything off. Moving back to the outlet box you will have wires coming out, at least one cable, there is rules about how much wire can be in a box, if you see a whole bunch of wires stuffed in there and it looks like quite a bit of mess, it`s probably a good idea to call an electrician. If you take apart the outlet and inspect it you will see that on the side it has terminals, two brass terminals and on the opposite side two silver terminals. In addition to those two terminals, you will see on the back of newer outlets four little holes that are designed to push the wire in and that is supposed to hold it.
You should never use this things, they are an awful idea, they are used basically for a cheap way out, if an electrician is doing a lot of work he can jam the wires in there and call it a day, and it just takes less time and effort to get it done, but those wires tend to loosen up over time. You want to use the terminals on the sides of the outlet for provide electrical commissioning. If you do decide to replace your own electrical outlet, and not call a professional electrician, always make sure to check online for the switchboard manufacturers layout plan of the breakers and switch off the main breaker so you cut off the power in your home.