Start off with a clean line drawing of the head and hair. Use hard graphite to sketch and medium graphite to define lines.  Sketch in a circle with guidelines for the eyes and jaw.  Sketch in the eyes, eyebrows, nose and mouth.  Sketch in the bangs and any hair that is overlapping the face. Define the chin.  Sketch in the hair on the left side of the head.  Sketch in the rest of the hair.  Erase all unneeded guidelines and define the lines with an HB or F pencil.