When I started I could barely do one pullup. Now I do five sets of pullups in my favorite workout. I can currenly do up to six at a time and I'm still improving.
I looked up how to improve and here's what I got:
I started building up strength with inverted rows and negative pullups. Go ahead and google em for some tips.
Inverted rows are kind of like pullups that you do with your feet on the ground. I used a railing which had my body mostly horizontal, and also the lowest pullup bar at the playground, which had me just leaning back a bit. I could do a lot more reps that way, but it does help build up your strength.
Negative pullups (and hangs) are the other method I used. That's just where you use a jump start to jump up to a top of the pullup position and THEN engage your muscles to hold it. Then I would lower myself as slowly as possible, trying to pause halfway down.
Nowadays I'm still using these methods to help compliment my pullup workout. I'm trying to break a plateau (I can't seem to break 21 in five sets) by using some weights in a backpack while doing some of my pullup sets and also a couple long negative pullups with weights.
I agree with Patrick. Negative pull ups are the way to go. Try and lower yourself as slow as you can after jumping up to the bar
I use all of these techniques: inverted rows.. weights ( I use a 20lb vest. The back pack I thnk would b a better idea because the vest is so difficult to take on and off through out sets ) .. negative reps ... and even resistance bands to ..I also incorporate some bodybuilding training method like rest pause technique or even go through the day an everytime I pass the bar I Do five reps...I find negative reps to work the best I think and also bar hangs and forearm work to help me keep my grip longer....