The first thing that stuck out at me was the fact that you use a pretty heavy line all around the figure, which flattens it. If that's your goal, then that's fine, but if you want to draw realistically you'll not want to 'outline' your figure.
Secondly, be careful that parts of the figure that are supposed to be straight are straight. For example, in the archery pose, his arm is seriously bent in an impossible way.
One way to combat issues with limbs bending incorrectly as well as proportion is to step back from your drawing often. In the picture of the man sitting, the hands look too small. That usually happens when you're so busy focusing on that particular area that you lose a sense of the picture as a whole. So again, step back from your drawing often.
You've got a good start going here. I'm not sure what your assignments were, but at this stage I'd spend a lot more time working on basic proportion and form. That means do a lot more drawings and don't spend so much time on the "shading" and details (veins, etc.). Lay out the figure, when you get it right, move on to a new pose. Repeat, repeat, repeat. Step back often as danteort says.
Ahh the ol' "Step back from what you’re working on..." comment... I scream it at myself in my head repeatedly, and yet it seems I still manage to get sucked into a small area and not view what I'm working on as a whole. As for the outline subject.... This is something I've been trying to change. I keep trying to remember to define with contrast; but can only rarely put it into action. I will try to drive the point home in my head even more.
The wrist on his arm was a bit warped, I fixed it in class last night, and I will post an update later today. Thanks a ton for the crits daneort.
The assignment is essentially a "long pose" spread out over 2 or 3 classes... So we're kind of set up to do finished pieces. We also do 4 quick poses at the beginning of every class, though; I just didn't post but a few of those. I've always had a problem obsessing over the details; my teacher has to step in and tell me to work the piece as a whole often. If you care to look...