Ha ha I have pictures of just about all of my work in steps like this just to show they are done in pencils and not photo shopped. You do when you 1st start trying to draw. Square by square. Me? No. Most of the time the squares are just to give you an idea of where your at in your work so you don't get lost or distracted. You can draw it square by square I do with the eyes or a face but not with hair or backgrounds Just where I want the focus point to be. When you draw you don't draw what you see you draw shapes and tones and never from a colored photo if you are using pencils
You see, I am not too good with having mental images. I can't draw like a horse just from my head. However, if its put infront of me, as if i am looking at it through a cameras viewfinder, I can make the most and more out of what is there.