I could start this by saying "Everything." Just having returned from a show at a charming museum in Ukiah, Cal, that had a rather large show of his work, I am once again reminded of: draw, draw, draw; be honest with yourself and the subject; simplify/really think about shapes.
A new book is out on his life, and again I am in the painting spirit. His thoughts spoken over 60 years ago, at the end of his life (1946) still ring true. Be honest with yourself...and paint honestly! Seeing his work inspired me to simplify this painting.