I have been stuck at 8 reps on pull-ups for sometime. I found a way to move through the road block and increase reps by using the idea of muscle "time under tension."
From the pull-up starting position which is arms fully extended,
- Pull-up to 1/4 of the full movement and hold for 5 seconds;
- Pull to 1/2 position and hold for 5 seconds;
- Pull to 3/4 position and hold for 5 seconds.
- Lower to 1/2 position and hold for 5 seconds;
- Lower to 1/4 position and hold for 5 seconds;
- Fully release
This move equals 1 set. Do 5 sets resting no more than 60 seconds between each set. Once you are able to complete 5 sets, begin adding weight.
I have found that this is a better workout than just banging out reps on the pull-up bar.