So on this one I began as usual, but before I got very far I decided where I would crop the face and worked from then on just in that area. In fact, I taped a little frame made from an index card over the drawing as I continued to work.
Then at the end when I took the frame away I liked the effect! I find the ragged edges on three sides and the transition from "in process" to finished on the fourth side very appealing.
So now I don't know whether to crop it or not.