As I lifted this morning, I thought back to my lifting journey to this point. I think the biggest gains I made this year are in my back. I owe a lot of that to pull ups. These light up your entire back. Your lats handle the shoulder extension. Your mid traps and rhomboids are activated during scapular retraction. Your lower back will be engaged for stabilization. And your biceps will take care of elbow flexion. There's also going to be some core activation since you aren't seated like in a lat pull down.
Here's a simple technique suggestion. Think about getting your chest to the bar rather than just getting your chin over the bar. This will help you in getting control of the movement better. Also, think about pulling with your back rather than with your arms. This will activate your lats and prevent your biceps from taking over.
I'm working pretty hard on my arms and back because, Lord willing (it's always up to him!), in exactly two weeks from today I fly to Dallas and from there to Honolulu for 9 days of surfing. One spot I hope to surf again is Diamond Head. Though technically a part of Waikiki, Diamond Head is really a break of its own. Rather than being protected in the relatively calm waters of Waikiki (Mamala Bay), Diamond Head is located in more open (and deeper) waters. To surf this spot you first have to climb down cliffs to get to the shore, then paddle out until you hit the reef. This spot gets blown out from the tradewinds too. It always looks like a windy, soupy mess.
But should the winds die down, you're looking at the some of the best waves on the South Shore. It'll be super fun and really hard to get waves because most spots on the South Shore are crowded all the time. Don't mind that at all. Might even get some epic barrels!