When I draw heads, I like to first add a circle for the base of the head and a shield-like shape for the jaw. Then, I add two lines where I want the eyes to be, ensuring the line for the top of the eye is at the same level as the top of the ear, and the middle line is positioned where I want the midpoint of the eyes to be. When I draw the eyes, I make sure that they are the same distance apart as one eye between them. When I draw the mouth, I make sure it is on the same level as where the jaw curves.