I always start with the skull, focusing on bone structure and taking measurements from the models skull. Once I have it blocked out to those measurements I usually have a likeness beginning to develop. I sculpt the portrait, only the head, straight on, with little or no expression. This is easier for the model. Then once I have captured the likeness, I sculpt the expression I want and then turn the head to the angle I want for the finished portrait. Once that is done, I can then add the neck, shoulders and however much of the torso I plan to sculpt. Since I now have the angle of the head, the muscles in the neck and shoulders can reflect that angle. The last thing I add is the hair, the fun part that brings it all together whether it's short hair or long.