Hum is bad....
No matter where we are, Radio Frequency interference is there. In the worst case scenario, It could be severe enough that you could hear voices or music from a radio station.
More often, neon and fluorescent lights, dimmer switches, Televisions and all sorts of other devices can cause unwanted hum and crackling. High impedance guitar circuits are susceptible to this. Humbucker Pickups cut down on a lot of this. Learn more about how they do this here
While pickup construction and quality can have a major effect on the amount of RF interference, the rest of the tone and control circuit also has a major effect.
A man named Faraday learned that you could surround a circuit with metal and block unwanted RF interference. Using conductive tape or paint, you can create a "faraday cage" around your pickups and controls. This will minimize the amount of hum and unwanted noise in your guitar.
1. Using a conductive material, completely surround the controls and pickups
2. Ground the shielding material. Each portion of the shield should be grounded.
3. Make sure the controls don't touch the shielding causing a short.
The video below will give you more specifics and tips to shield your cavities and pickups where needed.
Does Shielding Affect Tone?
While shielding has no direct effect on the the actual tone of the guitar, depending on how noisy the guitar was before shielding, you may hear some subtleties that were masked by noise. Try it.
It is a very cost effective modification that you can do to your guitar that can make a massive difference in your playing enjoyment.