just ask your teacher why it isnt the right way from his point of view. none of us can tell you why he said that.
im personally working by what cola described... but that does not neccessarily mean its the right way for you, or your teacher. youve got a teacher... exploit that...ask questions.
theres no easy way to drawing.. youve got to make it work the way youre able to...
"Have only 4 values, but all the edges you want."
"To any man who has slaved to acquire skill in his art, it is most irritating to have his ability referred to as a 'gift.'"