Grab a chin up bar with your hands a bit wider then shoulder width apart. Bend your legs so that your body is hanging from the chin up bar.
Straighten your arms and let your lats stretch. Hold this position for a second. Arch your back slightly and pull yourself up to the bar until your chin is just over the bar. Hold this position for a second to maximize the peak contraction. Slowly lower yourself to the starting position. Repeat.
Tips - you can vary your grip to work your back from different angles. (i.e. wide grip, narrow grip, overhand, underhand, etc.). If you have trouble gripping the bar you can use a pair of lifting straps and strap your hands to the chin up bar.
source: www.leehayward.com
