Originally Posted by Off Road
Ladders work really well. I posted another method a while back that really got my reps up (from 6 to 11) in a short time. It basically used heavy singles and doubles with heavy db rows.
Rows do a good job of retracting the scapula and training the external rotators of the humerus. In the pulling process, the lats are stimulated and this has positive carryover into pullups. That's one of the reasons I feel rows are such an important exercise. Deadlifts, rows, and pullups all compliment each other.