Splitting humbucker coils
If you look at the Tele wiring diagram above you will see that when the tone control is pulled up the lower lugs are engaged and the finishes for the bridge pickup become the "hot" lead. Ground stays at ground, that means the bridge South coil is engaged. Simultaneously, the right side lugs connect the finishes for the neck pickup to ground, making them the negative lead. Hot stays hot and you have the neck North coil engaged. When the neck North and the Bridge south are used together (the middle switch position) they are hum-canceling because they are reverse polarity, wired in parallel, out of phase.
On most humbuckers, the coil with the adjustable poles is South-up, you can check by using a compass. The North needle will be attracted to the South-up pole and South will be attracted to North. My Apex Humbuckers do not have adjustable poles, but North-up and South-up coils are labeled on the bottom or you can use a compass to check.
You can have a lot of fun getting some different sounds out of your instrument just by wiring it differently. One of my favorite websites for wiring diagrams is www.guitarelectronics.com.