Focus on pull-ups. Use different grips such as wide overhand, medium overhand, close grip over hand, medium underhand, close grip under hand, neutral grip with your palms facing. Also switch up the rep speed such as slow reps or fast reps. You can add weight or do pure negatives when you can perform any more positive reps. Using these different techniques allowed me to be able to perform 52 pull-ups non-stop and I can get about 12 good reps with three 45lb plates hanging from a belt. Negatives are really effective when you can only perform a few pull-ups at a time. Recently I've added a intense routine I do. Basically I perform 10 sets of 10 reps with only 20-30 seconds of rest inbetween each set. Even though I can perform more than 10 reps, I only do 10 on each set. With the short rest periods, by the time I get to the 10th set, I actually have to give it everything Iv'e got to reach the 10th rep. My lats get full of blood and are on fire when I do this routine. 10 second negative for as many reps as possible are really intense also. The variations of pull-ups you can do are limitless, well at least for me.