I'm slowly working on my next project, which will be an Alternators figure this time, and as with my last fan character I'm using my own sculpt. I've never worked with a ball jointed neck before, and I'd appreciate any advice on how to go about forming the socket in the head.

Thanks in advance :]

 

If you have a rotary tool (Dremel or similar), best bet is to get a set of those round burrs (like balls on the end of the shaft).

First drill down to the depth you need the socket to go, just to make it easier on the ball bit. If you have some cylindrical burrs you can use that to widen the hole to accommodate the shaft.
Select a head roughly the same size as the shaft of the ball joint you want to use, and use that to get the shaft hole the right depth and width. Once it's at the right depth, you can start to wiggle the ball around in the hole, widening the hole on the inside.