In this wiring, the source is at the switch and 3-wire cable runs from there to the fan/light. The switch controls the light and the source is spliced through to the fan. With this arrangement, the fan is controlled by a pull-chain on the motor housing and the light is controlled with the switch. The neutral and ground wires are also spliced through to the fan/light.
In these cases, it should be wrapped with electrical tape to mark it as hot. The ground wires will be green and/or bare copper. The ground should be spliced with a short piece of wire and connected to each device and outlet box that has a grounding terminal. In these drawing the brass colored terminal represent the hot side of the device and the silver colored terminal represent the neutral. Ground wires and terminals are in green.
Here a gfci receptacle is added at the end of a row of duplex receptacles for single-location protection. The first outlet is connected to the source and 2-wire cable runs from box to box. All wires are spliced with a pigtail at the devices to pass current from one to the next. The load terminals on the gfci are not used and it does not protect the other receptacles in the circuit.
This gfci wiring provides protection to a duplex receptacle. By connecting the load terminals on the last gfci, the receptacle is protected and can be used just as if it were one of the gfci receptacles. One ground fault circuit interrupter at the beginning of the circuit can be used in the same way to protect multiple, subsequent receptacles as illustrated in the diagram below.