Ahhh Lavander-town, my favorite youtuber!
To create a dynamic pose it's all about the line of action that was illustrated in the previous answers, though you also need to have a good understanding of anatomy to make it all fit for the better!
What helped me the most into drawing poses was probably doing gesture drawing like super-duper helpful! After sketching down around 400 poses i was able to have a better grasp on anatomy and dynamism ^^
I also suggest you to take a look at Proko's videos about the gesture drawing course on youtube, he really helped me A LOT!
For books i suggest (and i've read): "Anatomy for sculptors" and "Force" (can't remember the author though...)
One is about how to make a proper anatomical construction and the other one talks about the importance of giving characters the right flow of the pose, movement and dynamic force. A nice book for those who want to make animations!