Placing One Eye Center in a Composition
One technique that is commonly used by master artists and photographers when composing a portrait is that they will place one eye of their subject dead center in the frame. It has been said that by placing one eye center "the portrait tends to follow you around the room." To give an example, in the photograph below by Steve McCurry notice how the young girl's right eye is perfectly centered within the compositional frame. In this particular example, placing one eye center adds a dramatic visual effect because of the subject's intense stare at the viewer.
Painting above by Michel Jacobs demonstrating placing one eye centered in a composition - designed in a root 2 Dynamic Symmetry rectangle. To learn more, see the book The Art of Composition: A Simple Application of Dynamic Symmetry.