Pay careful attention to placement of the eyes. If drawing without any aids, refer to the key 'landmarks' of the face, checking the angle and distance of the inner and outer points of the eyes in relation to the ears and nose. When you sketch a straight line through the eyes, base of the nose, mouth
and brows, you'll find that they are in correct perspective or parallel.
When I begin drawing a portrait, I usuallysketch this structure, using construction lines to indicate the planes of the face, place the pupils and draw in main lines of the lids and brows. Including wrinkles and lines at this point can help provide reference points.