Step 4: Inspect Receptacle Wiring
Take a look at the receptacle to understand how it’s wired. Some outlets simply have one hot (black) wire and one neutral (white) wire. The black wire should be attached to a brass or gold screw, and the white wire should be attached to a silver screw. There may also be a bare or green ground wire attached to a green grounding screw on the receptacle.
Other circuits are wired in daisy-chain fashion from one to the next, with one set of black and white wires leading into the receptacle, and another set leading out to the next outlet. Still others might be wired on separate circuits, with entirely separate wires feeding each of the two outlets – that’s why voltage testing is so important.
If you have multiple wires coming into your receptacle, use bits of masking tape to mark which wires are attached to which screws, because once you disconnect them it will be hard to remember what goes where! On complicated hookups, draw a diagram, or take a picture of the wiring before disconnecting it.