All Single Coil and Split Coils:
The black wire is ground and the white wire is hot. The gray wire also goes to ground unless a buffered input preamp is used like an Audere, in which case the black wire goes into the preamp common and the gray wire goes to ground.
All Dual Coils and Humbuckers except Music Man replacement:
Series Wiring: Black = HOT. Green + Bare Wire = GROUND. Red and White together and taped off.
Parallel: Black and Red = HOT. Green, White + Bare = GROUND (Black and White are the bridge coil and red and green are the neck coil).
All Stacked Pickups:
White = HOT. Black = Ground. Red = Coil Tap. This means to run the pickup in single coil mode you need to short the red wire to ground and this can be done easily with a switch. For normal hum cancelling mode just leave the red wire taped off and not connected to anything. If there is a gray wire, see below.
*Where does the gray wire go? The gray wire is for grounding the pole pieces. In an installation with a buffered preamp (Audere) where the common out on the pickup needs to be separate from the system ground the gray wire will be ultimately connected to the sleeve on the jack. This can happen by connecting it to shielding foil, the bridge ground point, or the appropriate connection on the preamp. On a non buffered preamp, which is pretty much everything else, or a passive installation, the gray wire can simply be tied into the black wire and connected exactly where the black wire is connected.