Amateurs start by drawing each strand ot hair and finish with the outline for the entire head ot hair.
The first thing a Professional thinks of is the entire outline. Then he/she divides the hair into tufts by drawing lines. Shading and applying different areas of colors are deliberate ways of changing tufts of hair and the shape. The important thing is to pick out shapes for hairstyles from your favorite works and pictures that you think are good, and start drawing them.