Angela Cunningham, my cast drawing teacher at GCA told me that one should always think in terms of gradation, not to think in terms of dark or light or value, think in terms of “is it closer to the light, or farther away from the light”, which plane is facing away from light or closer to light, is is rolling quickly or slowly. ¬†Think sculpturally, put your marks in so that you don’t see any white spaces and you don’t see the direction your pencil is going. ¬†Always stay on the form so that you are focused.