There's million ways to mod your guitars wiring. The most common types are replacing exsisting yum cha cvomponents with top of the range units and adding switching options. I've listed some of my favourites.
You will be amazed at what a decent set of pickups can do for any instrument. I've replaced countless pickups both cheap and expensive guitars and basses and the result is always a better tone. It is important to choose the right pickup and I can advise in this are if necesary.
many production guitars use very cheaply built components and because you dont see them it is a great area to save on production costs. Upgrading the pots [volume and tone controls] with CTS copmonents top grade capacitors like spragues can really open up the tone. While in the area it,s alway a good idea to upgrade to heavy duty swichcraft output jack and switches.
Sheilding to reduce mains hum.
Lining the electronics and picking cavities with copper foil or conductive paint and star grounding is a good way to minimise mains hum. This is especially useful on guitars like strats and teles equipped with single coil pickups. Basses with single coil pickups can also benifit from sheilding.
Treble bleed or high pass filter.
This quick and easy mod helps keep the treble in the signal as you dial back the volume control. Most guitars volume control not only lowers the volume but takes out the bite making the tone muddy or thick as you roll it back. I know some players like this but many won't touch the volume as it dulls things off. The cap used in the mod can be varied to keep just the right amount of treble in. You can actually make the tone sound brighter as you wind it back if you want. It is a matter of tuning the mod to suit your pickups and guitar.