Hang from a pull-up bar with a supinated grip, allowing the shoulders to open completely. Initiate the motion by pulling the shoulder blades down, then pull your body up until your chin is above the bar and arms and shoulders closed as completely as possible.
 
Lower to a fully-opened shoulder hanging position under control and repeat.
 
Purpose
The chin-up is an effective, full range of motion vertical pulling exercise that strengthens the back, shoulders and arms. The supinated grip means more emphasis on the biceps relative to a pronated pull-up.
 
Programming
Generally sets of 6-15 are appropriate, with much higher rep sets with bodyweight for those appropriately capable, and reps as low as 1-3 for weighted sets.