I have started my model by the head. First I created a sphere and then using the moving brush I started giving shape to the head. Then using masking and the moving and inflate brushes I started giving shape to the eye holes and mouth. Then I created the teeth base and placed a new sphere in the eyehole to have an idea of the shape of the eye. Finally I closed the mouth using the move brush and defined a bit the lips with the Dam_Standard brush.