The Eyes

One of the most difficult thing to achieve in portrait is how the photographer can make his model looks into the camera the way he likes, and it is not that easy.  
As early as Cicera (106-43 B.C.) who quoted "Ut imago est animi voltus sic indices oculi" - the face is a picture of the mind as the eyes are its interpreter.  The Latin proverbs - "Vultus est index animi" or "Oculus animi index"  are usually translated as "The face is the index of the mind.  And it cannot be said better.
As a photographer to try to get the look I want, I will need to make my model totally relaxed and open so the window can open to allow me to see more, or I just get a window.