Make sure the capture area is well lit
Make sure that during Calibration, no other people are present in the volume except the actor.
Make sure that the capture volume is marked out clearly on the floor.
Check your surroundings and see if there are any mirrors in view of any cameras, this will be very confusing for the system and should be avoided at all costs, as additional actors may be detected with misleading locations.
Do your best to mitigate water droplets sitting on the camera lens if capturing in the rain, this will distort the image and impact the tracking.