To perform hanging leg raises grab a hold of a high chin-up bar (preferably with wrist straps).  With the arms and legs extended simply lift the knees up toward the chest contracting the abdominal muscles and return to an extended leg position thereby stretching the abdominal muscles. 

Hanging leg raises are almost always performed incorrectly.  Too often while performing hanging leg raises people swing their legs up and down, use momentum instead of the abdominal muscles and work their hands, forearms and hip flexors more than the abdominal muscles.  For this reason there are several products on the market to make hanging leg raises easier such as the Gut Blaster Sling and Ab Loops.  The Gut Blaster Sling and Ab Loops allow for a better abdominal workout because it takes the pressure off of holding your own body weight in position.  Allowing for total concentration of the abdominal muscles themselves.

However, if you desire visually appealing abdominal muscles it is necessary to follow a healthy fat burning program to rid the stomach area of its present level of body fat tissue.  Abdominal exercises do not and cannot spot reduce the fat from the stomach area.  Abdominal exercises only strengthen, tighten and tone the stomach area.