Local and national electric codes in the United States require exposed metal parts in an AC electric circuit to be connected to ground to avoid physical contact with dangerous voltage in case electrical insulation fails. It is your responsibility as a homeowner to see to it that each circuit is properly grounded. Keep your 110-volt or 220-volt AC circuit safe by learning how to fix ungrounded electrical outlets.
Open the cover to the electrical panel. Look at the electrical panel legend at the back of the panel door to find the circuit breaker that controls power to the outlet you will be working on. Flip the switch of the circuit breaker to its "Off" position.
Set the dial of your multimeter tool to 110 volts AC range. Insert the metal tip of the red probe of your multimeter into a vertical slot on the outlet, and insert the other probe into the other slot. Look at the multimeter reading. If there is no movement in the multimeter display or the needle, this indicates that the power is off and that there is no electricity flowing through the wires.
Unscrew the faceplate of the outlet and slowly pull the faceplate away from the wall to expose the terminal screws behind it. Place the tip of the red probe of your multimeter against the black terminal screw on the side of the outlet, and place the tip of the black probe against the silver terminal screw. Check the multimeter -- no movement or reading on the multimeter is an indication that there is no current in the wires.
Look for a green or bare wire on the outlet or inside the cable box. Carefully pull the green or bare wire out of the box. Strip off 1/2 an inch from the tip of its insulation with a wire stripper. Loosen the green ground terminal screw at the bottom of the outlet and hook the green or bare wire around it. Tighten the screw clockwise to secure the connection. Reattach the faceplate to the wall with a screwdriver.
Use a ground wire with equivalent amperage as the circuit breaker controlling the circuit you're working on if there is no green or bare wire inside the outlet box. Turn off the main breaker switch in the panel. Run the wire from the wall outlet to the panel box. Strip off 1/2 an inch of insulation at its tip and insert it in a vacant slot on the ground bar inside the panel. Tighten the ground bar terminal screw to secure the connection.
Strip off 1/2 an inch of insulation from the tip of the green wire coming from the outlet box. Hook it around the green terminal screw on the outlet and tighten the screw to secure the connection. Wrap electrical tape twice around the sides of the outlet. Screw the outlet faceplate to the wall, using a screwdriver.
Turn on the main circuit breaker switch in the electrical panel. Turn on the circuit breaker connected to the circuit you're working on. Plug an appliance into the outlet to test it for power.