Turn off the circuit breaker, remove the fuse or turn off the main power supply to the house before undertaking any electrical work. If you have an old fuse box, each fuse represents a different circuit. In newer electrical systems, fuse boxes are replaced with breakers, which serve the same purpose but can be switched on and off rather than replaced.
Replace outdated outlets that lack grounds by removing them from the walls. You can tell these outlets because they have two elongated holes but no round hole between them. The round hole accommodates the ground prong in a grounded plug. All outlets now have three holes in them. Remove the plate, pull the old outlet out of the wall and disconnect it from its wires.
Feed new, grounded wire from the fuse box or breaker box to the outlet that is being replaced. In a finished house, this is often the most difficult part of a job because you have to get the wire through the wall. This can involve either fishing the wire from the basement up into a wall using a special hooking tool, or cutting pieces out of the walls to get the wiring through.
Feed the wire through the opening for the outlet and attach a new outlet to the wires with needle-nose pliers. Attach the black (live) wire to the gold screw on the side of the outlet, the white (neutral) wire to the silver screw on the side of the outlet and the bare (ground) wire to the screw on the bottom of the outlet.