Well, you are doing a good job so far. Just some areas need tweaking or remodeling. For instance the frontal view of the image has some irregular faces, and poles, giving you undesirable results. I have marked some of them in a single red circle for you.
You could also try selecting a few of the verticies on the cheek area and smooth them out in the editing panel those areas are marked with red and orange
Like I said you are doing well, just fix up a few of those areas and you will be getting even better results.
Important for this type of modeling is try, try and try again. One school that teaches modeling makes the students model a human head, then delete it. Model it again and again and again, every time deleting the file on the students. No matter how good the models were. Why? because the more they do it, the better they get at it and the more they recognize where they went wrong.
I am not saying to delete your file, just once this one is done, start another one and see how much more efficiently you can model those complex areas.
Here is a link to a great tutorial that goes into depth about the modeling process of a human head. The author uses Silo, and it is accomplished using box modeling while yours is polygon modeling. But everything is transferable to blender and the priciples apply just as well to box modeling as it does polygon by polygon modeling.
Link to the thread. http://www.subdivisionmodeling.com/forums/showthread.php?t=2347&highlight=devil
You will need a Techsmith codec to view the tutorial, since the author uses Camtasia. Here is the link to that codec.
Look forward to your posts. Keep it up!:yes: