Position
Place your hands on the bar in a position that when your upper arms are parallel to the floor they will form an approximate 90-degree angle with your forearms. Hang or stand on a support and lean back slightly. Hold the bar with your elbows slightly bent and elbows pointed out. Pull your shoulder blades down and together, creating a natural arch in your lower back.

Technique
Contract your lats, pulling your elbows out as your body rises. Pull your body up until your upper arms are about parallel to the floor. Keep your shoulder blades down and together, maintaining a natural arch in your lower back. Hold, contracting the lats, and relax your hands and arms as much as possible. Lower your body slowly to the start position. Repeat.