Sketch the face onto a piece of paper, to scale if possible. Draw a line that goes across the middle of the face horizontally. This is the line that the eyes must line up on. Divide the middle line into five segments. A typical face is five eye-widths wide, so the eyes should fit into the second and fourth segments. Add the mouth and nose.
Sketch the same design onto your piece. This is difficult to do with some materials, so you may need to improvise. If your drawing is to scale, you can use the ruler to measure parts of your drawing and compare to the carving to make sure that your sculpture is proportional at every stage of the carving process.
Roughly carve the face, leaving shallow hollows at the eyes. Do not carve too deeply at the eyes, but be sure that the ridges above the eyes are defined.
Draw the eye shape again at each eye, checking to make sure that they are the same size. Shape the eyes as though they were a ball embedded into the face. Leave a shallow hollow underneath the eye and a slightly deeper one on top of the eye.
Carve a shallow groove over the "ball" shapes to indicate the eyelids. The corners should fall at the outer edges of the ball. Carefully remove a small amount of material between the "lids."
Mark a place for the pupil. It is important that the pupils on each eye face the same direction, so you may need to re-mark it several times.
Carve out the pupil deeply enough that the pupil appears dark.
Mark a circle around the pupil to imitate the iris. Carve a shallow groove over your mark.