One of the fun things about building electric guitars is wiring them up. Factory wiring tends to be simple, minimizing the amount of fussy handwork required. Many manufacturers keep strictly to 'classic' designs, seldom if ever changing anything. These designs are generally simplistic, often crude or even stupid, and sometimes outright flawed. There is no need for you to do this. I don't. Here are some of the things I have done over the years. I don't claim to have invented any of this, although some of these schematics I have never seen anywhere else, and had to derive them myself.
Multiple guitar pickups can be wired either in parallel or in series. Series gives a fatter sound, parallel gives a thinner sound. Almost all guitars have the pickups wired in parallel. That is why combinations on a single-coil instrument don't really build over the individual pickups. Pickup combinations on a Strat are known as 'quack' for their thin sound.