I scale the extruded edges to shape the eye and mouth. Another way is to make the face components then attach them to head.

You can find many great tutorials in WWW.3DTOTAL.COM to model components of the face. There is a way to see the result of the polygon object in smooth mood as you adjust the vertices on the original head. Make a Duplicate of the head.(EDIT>DUPLICATE) Select Connection Editor.(WINDOW>GENERAL EDITORS>CONNECTION EDITOR) Load the Shape node of original head to outputs window by clicking the Reload Left button then load the Shape node of the duplicate model to the input window. connect the OutMesh from the output window to InMesh from the input window. Smooth the duplicate model.(POLYGONS>SMOOTH) Now when you adjust a vertix on the original model you can see its result in smooth mood on the smooth model. (duplicate model)