Ever experience the frustration of a guitar rig that hums madly the moment the player stops touching the strings? Ground lifts often don't work, and neither does repositioning the player's position relative to any nearby magnetic fields (say, for example, your monitors).
Next time you come across this problem, try this simple solution:
Find a discarded guitar string, or a spare patch cable, and tape one end of it to the guitar's bridge. Make sure that it's not in the player's way! Then take the other end and tape it to the player's side, directly on his or her skin. Now even when the player removes his hands from the strings, the instrument is still grounded to him via the bridge!