Identify the wire your wish to test. In home A/C (alternating current) systems, separate a small amount of shielding from the cable you wish to test, then separate the wires so each one is isolated. Electricity may travel in opposite directions in individual cables, cancelling each other's magnetic field out.
Set the dial on your meter to measure A/C or D/C current in amperes (Amps). This may be indicated with an "A" followed by a horizontal line with a dashed line under it for D/C, or a letter "A" with a sine wave after it for A/C.
Clamp the meter over one wire only. Clamping the meter over more than one wire will give you an inaccurate reading.
Read the display on the screen. This is the amount of current flowing through the wire. If no current is measured, there is no flow of electricity.