Remember also, for some switching arrangements, you need to separate the pickup ground (black wire in the OP's picture) from the baseplate or shield ground (bare wire in the OP's picture).
A classic example would be a "lipstick" neck pickup in a Tele and a 4-way switch.
The baseplate or shield still needs to be grounded, but you should install a third wire, a separate ground, from the baseplate directly to a pot casing.