I have a Neville Stratocaster copy that I have used sandpaper on to get a vintage look (not a good idea). I have also drilled a hole in the head because I wanted to fit a two inch screw in there but the wood was to hard. It had a humming noise when plugged into the amp (not the good kind of humming noise).
So I decided to open up the top of the guitar to see if there was something I could modify in there. I discoverd that there was a lot of dust in there so I used a vacumm cleaner to get it out. When I had done that I plugged the guitar into the amp to check if it worked after the cleaning, it did! I also heard that the humming that the humming noise had disapeard.
I asked a couple of friends and I also went to a music store and everybody said that a little dust really could interfere with the microphones.
I tried this on my friends guitar to, the sound of that also got clearer. My advice is to open up your guitar and remove all the dust inside if it's starts to lose it's output level or starts to humm.
One other thing I have done to my guitar was to use sandpaper on the back of the neck because it was starting to get sticky after all the hand sweat. The guitar got easier to change grip and it didn't feel so sticky to play it. I also smothend out the edges on the neck, it makes it easier to reach the high notes.
You can also open up the back of the guitar and adjust the springs, usually it should be three sptings, but on mine somebody had removed one spring. So my guitar doesn't go all the way back, that means that I can use my whammy as a Floyd-rosewood kinda whammy.
Back to the springs, the springs should be positioned like a triangle, otherwise the whammy wont go all the way back.
That's all I wanted to tell the world!