How to Reduce or Eliminate Hum
Generally speaking, there is nothing in a guitar that actually generates hum, generally you can assume that the hum is being induced into the guitar, or it is being added to the signal of the guitar.
Experimentation is your friend. Here are some possibilities –
RECEIVING BROADCAST HUM
There is something in the environment which is “broadcasting” RFI in the room where your equipment is located. Common sources of Radio Frequency Interference include motors (vacuum cleaners, refrigerators, and automobile distributors), and transformers (high-intensity lamps, fluorescent lights), and from big magnets like speaker coils or television sets. The sound from autos are likely to vary in frequency. The sound from lamps and lights and refrigerators are likely to be be consistent, and at 60 cycles per second, which is what we normally call ‘hum.’
The RFI can be picked up either by strings (antennas) or by pickups (coils) as the signal is induced into the circuit created by the guitar and its parts, or into the cord (usually not possible if cord is properly shielded on both the guitar and the amp end), or into the amp, and then …