Some of these resources are ones I've linked to before, but not all of them.
That is a forum post on EXRX that lists a lot of pullup resources. If you are trying to improve your pullup or get your first, there is a lot of good information for you.
I'll end with one cue that helped one of my clients achieve her first pullup:
Instead of pulling yourself to the bar, drive your elbows back and your chest up. This will usually accomplish a couple of things:
- you'll squeeze your scapula (your shoulder blades) together, which tightens up your back.
- you'll initiate the movement from your back, not your arms. This takes advantage of using your biggest and strongest muscles (the latissimus dorsi aka lats, generally) to initiate and then your weaker muscles (the arms) to finish the job.
- you'll more naturally pull through the bar height instead of to the bar height. This is important because if you have trouble finishing you'll have some momentum from the bottom of the pull. Nothing wrong with firing the muscles hard and propelling yourself up. You can work on ultra-slow reps later once you've gotten a regular pullup.
Nothing I know of feels nicer than a good smooth pull up to the bar; this cue might help you get there. If not, go read that forum post and the attached articles!