If you're going to pull yourself up from a hanging position, you'd best learn how to hang first.
Scap pull-ups are really good for people who have trouble activating their lats (which should be the first move you make in a pull-up). The ability to hang with straight arms, and then pull your shoulder blades down your back, is an excellent way to learn how to initiate a pull-up with your lats and make your back stronger for pulling.
Use a strong towel that's long enough to hang down, over the bar, on both sides. Without lifting yourself off the ground, hold on to both ends of the towel to make sure its strong enough.
The towel pullup is a completely different exercise from the pullup and most other pulling exercise since it puts as much demand on the forearms as it does on the large muscles of the back and arms. To get used to it, start by gripping both ends of the towel together with a baseball bat grip. Let yourself hang from the towel for ten seconds. Take a rest and then pull yourself up so your elbows come to a 90-degree angle and hang from the towel again.
Even though you're still using the "usual" muscles to do a towel pullup, chances are that your forearms are going to feel most of the pain since they are probably not used to an exercise of this intensity. So before moving on to the next step, stretch your forearms by holding your hand straight out in front of you with your fingers facing up. With the other hand pull the top of your palm toward you. Repeat the stretch with the other hand.
Start the towel pullup from a dead hang by gripping the towel and then lowering yourself until your arms are straight. In a controlled but explosive movement pull yourself up until your chin is above the bar. Slowly lower yourself back down until you get to a dead hang. Repeat the exercise for as many repetitions as possible and then stretch your forearms and back afterwards.
take it slow & don't overwork the towel grips/pullups. Many ppl are plenty strong enough to do pullups but don't have the grip strength, and overworking your grip can very easily result in tendonitis
Don't Pull up with bent hips and knees, or pumping your way up.
Don't shrug the shoulders and drop the chin to the chest while pulling. Trust me - this makes you weaker, recruits the wrong muscles for the movement, and might give you a nasty headache. And it ain't pretty to look at, either.
