Statue of Sir Walter Watson Hughes in front of the Mitchell Building, University of Adelaide.

1. The first thing you need to do is draw an egg. If you look at the head from the front it is shaped like an egg. Many people I know actually begin by drawing an egg, as you see here when they are drawing portraits. Next you need to draw a vertical line in the centre to help you to place the features symmetrically. it also helps to draw horizontal guidelines  to locate the features on either side of the vertical centre line. (More on the guideline can be found here)

2. When you draw an actual head over the egg, you can see how the guideline work. The eyes are midway between the eye and the chin. The line between the lips is about one-third of the way down from the tip of the nose to the chin. the ears fall roughly between the guidelines of the eyebrows and nose.

3. when  you add tone it still helpful to visualise the head as an egg. From left to right, you can see four tonal areas that flow from light to halftone (or midtone, middletone) to dark (shadow), so when you start adding tone just follow the same sequence of tones.

The graduation of light, halftone, shadow and reflected light is ‘most’ obvious on the forehead, cheek, and the jaw. but you can also see it in the eye sockets and on the underside of the nose.