Block head

Here is Block Head. This was a shading exercise showing the contours of the face drawn with three different types of pencils. 

Also notice the sides of the face. This is something artists do all the time that nobody notices. On the right side of the face I wanted to highlight the bones so I put dark next to it. In between the dark I then have to put light. When you do this you then HAVE to do the opposite on the other side. Why?... Because my teacher said so. 

The dark next to light allows you to draw the viewers eyes to where you want them to go.  Dark next to dark keeps the viewer from looking in that area. So most likely your eyes will be drawn to the right side of the drawing because of the larger contrast.