Good exercise for pull-ups

Pullups really require no assistance exercises. Use various grips (overhand, underhand, neutral, wide) and add weight when you can.

Horizontal pulls, rows, will largely work similar muscles except they also have a scapular control component. There are lots of ways to do rows: DB rows, barbell rows, cable rows, inverted rows (pullups with your legs elevated to pullup bar height, the opposite of a pushup).

If you are stronger (and ambitious), you could begin working on the front lever family of exercises, either static holds or rep based work. The front lever family of exercises can be taken to very, very high resitances and is considered a horizontal pull. Not to mention it is one of the coolest things the human body can do. The front lever family includes static holds, lever rows, ice cream makers, and pull throughs. In general though you aren't strong enough to even do the easiest exercise in the front lever family until you can do about 10 pullups (in a single set).

Have you done any TRX stuff? It doesn't require as much strength as just a straight pull-up, but you can really isolate the smaller muscle groups in your upper body and strengthen those (which will in turn, strengthen your pull-up).

I have never heard of a plan to increase pullup numbers that includes isolation work.

If you want to do lots and lots of pullups, do lots and lots of pullups, weighted and unweighted.

The only assistance exercise that I know of that adds to the pullup progression (that isn't doing pullups/chinups) is rope climbing. However this is not particularly useful for 2 arms pullups. But, it you are looking to learn to do one arm chins, once you can bang out 20-30 pullups, no leg assist rope climbing will be one of the best things you can do to progress toward one arm chins. Progressively weighted pulls are useful too, but the nuances of single limb vs. bilateral work make rope climbs a little more effective.

You can look at the muscles hit by doing pullups, and do other exercises to build the musculature of those muscles. It wouldn't be a strictly 'build your pullup' plan, because as Waldo said for that you should just do more pullups and pullup variants, but it could increase strength and build mass allowing for further development.

http://www.exrx.net/WeightExercises/LatissimusDorsi/BWPullup.html

So basically trap stuff, but building your whole back is a good idea anyway:

http://www.exrx.net/Lists/ExList/BackWt.html

Some arm work wouldn't hurt either.

waldo56 - If you want to do lots and lots of pullups, do lots and lots of pullups, weighted and unweighted.

^^ this
Grease the groove, everytime you pass the bar do as many as you can.
When doing your workout add weighted pull ups and concentrate on good form. On your last set do unweighted and just do them to failure. Also negatives are a great way to go to increase your strength and grip. Slowly lower yourself from the top all the way down to full hanging and then pause and reset i always finish on these!

As for the pain your feeling, do you do many back stretches? I would recommend foam rolling on that specific area
Between pull up sessions work your other back muscles doing Bent over rows and lat pulldowns even Cobra to work your traps and rhomboids.

Good read thanks guy!!!!! I can only do one LOL i am wanting to do 10 someday ..