Fitness

If you are struggling to actually begin and pull up from a dead hang then build your strength first by concentrating on negatives.

Stand on something and start in the top position and then lower yourself down as slowly as possible. Try and be as controlled as you can, the slower you can go, the better. This is better than just hanging there struggling as failing to be able to pull up will not build any muscles where as this will slowly build the muscles you need and then as you get better you can transition to actually pulling up.

Even if you can do a pull up doing the negative slowly and in a controller manner will more efficiently build the muscles needed. If you just drop back down you are wasting half of the movements potential :)