How to learn character sketch?

The head is square, the neck is round, the chest is square, the abdomen is cylindrical, and the greater trochanter of pelvis is trapezoidal. The pubic bone is located at 1/2. According to the length of the head, the second head reaches the nipple (the lower edge of the scapula), the third head reaches the umbilicus (the superior iliac spine), the fourth head reaches the perineum (the bottom of the hip), the fifth head reaches the middle of the knee (the femoral joint fossa), and the seventh head reaches the sole of the foot. Composition lies in whether the draft can quickly and simply identify movements, bone points, perspective of five senses, hand-blocking face and foot direction. Leave more white space in the direction and less white space on the top of your head. It's more accurate than looking for a type.