In my college years in Cal State LA, one of the most memorable art classes was my life drawing class. Other than being able to stare at nude woman for a prolonged period of time, it really is one of the best courses you can take. No matter what your skill level is, the practice of drawing from nude models is a priceless exercise in my opinion. You’re never too good or too old for it.
But anyhow, the point I wanted to make here was that one thing that my life drawing teacher taught me was to draw the left side first. It’s not rocket science as to the reasons why, if you’re right handed, you can see what you have already drawn. If you’re left handed, you would start on the right side first. I’m not saying to draw completely one side first with a clean dividing line, but just as a start. I have started every drawing this way since that lesson.
I am right-handed. Here’s a drawing that I have just started. As you can see, especially with faces, it really helps to start on the left first. I can almost remember what he told me exactly on drawing the left side first, “…even if you have other ways of drawing, just try it.” I did and I never looked back.