A series of guidelines has been drawn on the figure to the left to show the approximate position of each part of the face. Although it is not absolutely necessary to start with these lines, it will help you in your initial sketch. The center line runs from the center of the forehead, through the stem of the T-Zone, and helps greatly in lining up the mouth, eyes and the nose. The center of the mouth and nose should be on the line, whereas each eye should be equidistance, about half of the eye width away from the center line.
The bottom of the eyes are approximately half way between the top of the head to the chin. The top of the ears are on the same horizontal line as the eyebrows. Approximately half way between the eyebrows and the chin is the bottom of the nose and about a third of the way from the bottom of the nose to the chin is the mouth.
The facial proportions of a child is also different from that of a full grown adult. The nose is shorter in that of a child than that of an adult. In this case the eyebrow line will be half way between the top of the head and the chin. Each of the other features: the center of the eyes, the bottom of the nose and the mouth, are all a quarter below the eyebrows and the chin.
Keep in mind that every person is different, and although these points are true in many situations, don't be afraid to break the rules.