Oh boy, I struggle with that too tbh! What I do is look at references and often go for a feeling like “this looks nice” and be my own critique.
I don’t do this that often anymore but you can try to decompose in geometric shapes/basic lines some poses you find interesting (either be in the internet or magazines~) what I think helps the most it’s the movement lines which, I drew red in these examples~~
Proportions may be the basics but those can be different for each drawing style, still I do recommend to study some anatomy and practice a lot!! Try to start with something simple and not to complicated like some torso pics and don’t be afraid to look at references or to do mistakes, we all are learning so it’s totally ok!
Here more stuff and as you may notice, not all of them have the same proportions but somehow they look “proportional” and since I’m still not confident enough in complicated poses, these are some simple ones :3
Also you can try simple skeletons with just circles and lines, then you can start building the pose from that.
Hope this helps you! I’m not that good explaining things