The neck begins with the creation of a rough Mahogany neck block. Essentially you have to make a few angled cuts, create a rough headstock, glue on a huge block of mahogany for the heel, square it all with a plane, and then begin shaping it into a neck.
Here's the headstock being trued with the neck shaft:
Here's the headstock being glued at a 15 degree angle to the neck shaft:
...and the rough neck blank in my "workshop" 
Next a channel is routed down the center of the neck to provide room for a metal truss rod. The truss rod is essentially two rods that, when tightened, bend together in one direction. With a truss rod embedded within the guitar's neck, it is easy to straighten the neck to counteract the forces of string tension. If left uncorrected, the string tension would bend the neck over time to the point where the strings would begin to be too high above the fingerboard to be comfortably played.
Now I'm beginning to rough out the headstock in preparation for applying the veneer: 
Speaking of veneer, here's the massive 2" thick slab of Amazon Rosewood that I got from AlliedLutherie that will provide more than enough material for some veneers and a bridge:
For the headstock veneer, I've decided to go with a book matched rosewood wedge arrangement, with a curly maple center wedge (to match me tail graft on the body), then I'll bind the headstock later with the same curly maple and black/white/black strips as used on the guitar body. I also want to include a small abalone inlaid emblem thingy at the top, but I haven't decided what it will be yet...
..and the veneer faced headstock waiting for final trimming, routing, and binding: