A 1:1 Ratio of Pull-Ups to Bench Presses
Lifters should be able to do pull-ups with as much weight – including bodyweight – as they can bench press, meaning that a 200-pound guy that bench presses 300 pounds should be able to do a pull-up with 100 pounds added.
A 1:1 ratio of pull-ups to bench presses should be the minimum. Let's assume that most males can do at least 7-8 bodyweight pull-ups, with whatever grip that's preferred. If you can't, and have been training for more than a few years, take this as a wake-up call that you seriously need to reconsider your training, nutrition, or both.
Once you've established a solid strength base, it's time to take it up a notch with isometric holds.
Pull-Up With Isometric Hold
Pull yourself up until your upper chest is level with the bar. Keep your chest puffed out, elbows pulled down and back, and focus on squeezing the shoulder blades together hard. Now hold it right there. The muscles burning in your upper back? Those are the ones you should be using on every rep of pull-ups. For now though, just squeeze harder.
Iso holds force you to recruit the proper muscles. If you don't actively retract your scapulae and try to rely on your arms to do the work, you won't last long. They'll also help strengthen the lower traps and rhomboids, which can assist with posture and ward off shoulder issues.
Do these with a pronated "false" grip. That's an overhand grip with the thumbs draped over the top of the bar. Research has shown significantly higher EMG activation in the lower traps during pull-ups as opposed to chin-ups, which emphasize the biceps. And using a false grip helps take the elbow flexors out of the equation so the back can bear the brunt of the work.
Try adding a 30-45 second hold at the end of your regular pull-up workout. Once you reach 45 seconds, add weight.