it aint that hard. (I drew it with my Samsung Galaxy Note: don't judge the quality).
you have 4 poles on your average superswitch. each pole has one lug for each position, and one common, functioning as an 'output'.
first pole.
bridge on the first three lugs, fourth lug: middle.. fifth lug is empty. common goes to the volume pot.
second pole.
first lug is empty. second lug: middle. last 3 lugs: neck. common goes to volume pot.
third pole:
second and third position: coilSPLIT (sorry I wrote the wrong word I know, sorry) wire of the bridge pickup. common goes to earth.
fourth pole:
third and fourth position: coilsplit of the neckpickup. common goes to earth.
voila.
it's that simple.
Some remarks though.
1: the coilsplit wire is the red/white thing you have to connect with seymour duncans, with dimarzio's it's the white/black wire.
2: I am not sure if the empty fifth lug on the first pole and empty first lug on the second pole have to go to earth perse. I haven't drawn that in, but it might be neccasary.
if it's a strat, or any guitar with more than 2 pots, you can even have the first pole having it's own volume pot and the second pole having it's own volume pot (no need for the other 4; they are just for coiltap, unless you want a spin a split, but I only think that would be cool if you have a gibson L5 kinda guitar with 3 pickups and 6 pots).
so many options, so little time.