Drawing the Eye
Whenever you look at a head, the eye will always draw your attention first. So if you are going to draw a facet, the eyes must be drawn correctly. There are some unique features of the eye that most beginner artist will get wrong. Once you learn the basic constructions of the eye, you will not make those mistakes again.
The Almond Shaped Eye
One of the most surprising features of the eye is the eye shape itself. If you are new to drawing, you most likely have drawn the eye as an almond shape. Though some people might have eyes shaped like an almond, that is not the vast majority. In general, the eye shape is skewed. You will see that in the video below. Don’t forget to check out books by Andrew Loomis. He is the best to learn from as his method is simple and precise.