I just recently tweaked a head and it was so frustrating to get it right.. I kept meddling with the position of the lips in relation to the nose and the general angularity of the face. I browsed through Details, GQ and Wallpaper and scoured down as many references as i can.. It looked slightly better afterwards but still something is not quite right.. then on my way home from work on the bus I saw this man with facial features that i wanted in my model.. I kept studying his face on the bus like a crazy pervert. I took out my sketchbook and secretly I started sketching him.. He was sitting with his back turned to me but every now and then he would glanced sideways and its exactly the angle that I needed. Its amazing how useful it is to have a real life model vs pictures from magazines.. Oh i wish I can have one at my disposal at any time.