Turn off power to the circuit
Remove the diode from the circuit if possible
Set the multimeter to diode test mode
Place the red probe on the anode and the black probe on the cathode
Read the forward voltage drop on the display
Reverse the probes
Read the reverse value on the display
Check for a normal diode reading
A good diode shows a forward voltage and no reading or OL in reverse
A shorted diode shows a low reading in both directions
An open diode shows OL in both directions