I think hands are the most difficult to draw. See if you can find decent, up close images of hands/fingers or even take a picture of someone's and just try sketching them. You don't have to attach them to an arm or anything, just practice it. Practice large and small illustrations of it, it helps, trust me. I'm not great at it, but I have the general anatomy of it down.
Try purchasing (or if you don't want to spend the money, just google these) an anatomy book with lots of sketches of the body. Attempt the bones first. When you get a general idea of the bones, it helps you get a general idea of the body. Attach the bones to other bones and it really helps you with proportions. I use rough outlines for body figures. I can show you some random ones, if you're interested.
