.............Old-time fighters used to do pull-ups while having a bag of rocks dangling from their nutsack with their trainers hitting them in the small of the back repeatedly with a baseball bat. They were tough then. :yep
Dunno, just keep on doing them. I started off doing 5 sets of 3, then got up to 5 sets of 5, and now I do 5 sets of 5, but with three of the sets as pullups instead of chinups because they're harder. Soon I'll be doing 5 sets of 5 pullups, then I'll start aiming for 3 sets of 10 or something.
i can do 20 in one shot, weighing 190lbs. Hardly ever do pull ups but im active enough at work to keep fit.