Think of bringing driving your elbows into your pockets.
Grab a pull-up bar with your palms facing your body. Lift your feet from the ground and hang freely ( A). Pull yourself up by flexing your elbows and pulling your shoulder blades down and back. Think of bringing driving your elbows into your pockets. When your chin passes the bar, pause ( B) before lowering slowly to the starting position. Try to avoid excessive swinging.