Pull-ups / Chin-ups keeps your shoulders straight and stiff like the shirt hangar. Its difficult to lift your own weight initially. Practice as few as 1-2 Pull-ups initially with the help of your trainer or a friend . Pull yourself up once or twice and keep hanging few half a minute . Practice this for two days and start doing the 2 pull ups yourself , try it hard , Hang free till you can do
2 pull-ups . Practise the same for three times a day .
If you are at the Gym ,you can do this between your chest , shoulder or biceps work-outs. If you find it difficult do 2 pull-ups , try adding more weight to the lat pull-down machine and practice lat pull downs. During this course you'll develop enough strength in your lats. Try doing pull-ups again the next day , you'll be able to do better.
Set your goal to do 10 pull-ups at a stretch in 5 weeks. Without a goal you'll hang endlessly :L
"Hang till you can do two pull ups"