The nose and mouth was built using the same methods as iv just described the mouth was a little tricky. I found that selecting polys and hiding the ones that were obscuring my view really helped, when i needed to work the inside of the mouth. Ill explain how i modelled the dangly bits in a while.
Here you can see the eye area after incorporating all the methods iv explained, after iv sculpted the eye i applied a meshsmooth to see what it looks like. One more thing you can do to the part you are working on is assign smoothing groups an crease edges, creasing an edge will sharpen the angle giving you a better definition.
I never used smoothing groups on this model, ill be showing you how to use them in my next tut.
To crease an edge. Click the minus sign of the meshsmooth modifier to drop the options for meshsmooth, looking at the pic you can see theirs 2 options vert and edge , click on edge option and then back to the viewport, select the edges of the yellow control cage on your model..Now you can play with the crease options "crease and weight" and watch as it updates real time. You can get a lot better definition now.
You can see were iv creased the areas under the eye.
When ever im making a symmetrical model i always delete half of it and then use the mirror tool and click instance so i only have to work on one side of the model and the instanced half follows my every move. giving you a better idea of what the whole looks like.