I'd say you should search for some reference photos/drawings of hands and arms from Google, and try to get hang of their anatomy, and how they work. It also helps if you try drawing a live model - ask a friend for help to pose for you. Just keep practicing, you'll get better! :)

....... I make Zack do to pose I need. Often. He looks at me like I'm crazy when I'm positioning his fingers!!!!

From what I've heard from so many other artists is you really just have to draw them over and over again. Hands are often an artists mortal enemy. I would suggest a hand and paw study (drawing only many different versions of the two). Drawing paws in between hands and mixing them together for a nice anthro look can keep it interesting. Best of luck :3

heres some from tumblr

http://gallowstyphoon.tumblr.com/post/73697826566/lifesbackwardandforward-a-glorious-fuck-ton-of

http://hi-fluent.tumblr.com/post/57954022709

http://art-references.tumblr.com/post/30146468656

http://thepirate-rudderless.tumblr.com/post/73436408312/hand-and-fingers-resource-tutorial-by