Our model today was Fiona Garrett. In my demo I talked about some of the basic facial proportions that are helpful to be aware of as you draw. It is important to remember that they are generalizations and will not replace the need to draw things as you see them.
Two of the most common mistakes in drawing portraits are: 1. Making the distance between the eyes and top of the head too short and 2. Making the distance between the eye and ear too short when looking at the face in profile. See the diagram below for the basic proportions that I talked about.
I also mentioned that when I draw a face always begin with a circle. The top of the head is a sphere so no matter what angle you see it at it will be a circle in a 2D drawing. After drawing the circle I find the center line of the face - a line that would pass between the eyes, middle of the lips and middle of the chin. Then I extend the circle with a jaw line to match the height and width proportions I see. Having these guidelines will make it easier to place the eyes, nose, mouth and ears. Eyes are especially tricky to foreshorten.