Probe the ground around a mole hill to find the run.  Upon pushing the probe into the ground, you'll find the probe 'give' if it enters the run.

Watch the video above for help on using a Mole Probe and Spade.

Once a run has been located, probe around the initial location to determine which direction the tunnel is running.  This will help to ensure you remove the turf correctly for the type of trap used.