When I shift-select my armature, I only get the head bone, none of the others. The "Automatic Weights" assigns all weight to the head bone. What am I doing wrong?
I'm pretty sure what's happening is your head bone is selected in Pose mode. So when you shift select your rig, it jumps to pose mode. That's ok for parenting, just make sure you select "Automatic Weights" and not the parent to bone option.