Hay~! You have really nice strating drawing. I think you really have something here.
Let's see. Uhm, I think you need to work more on their proportions. Their heads are too big for their shoulders and the rest of their body. And they seems to look too "stiff" although, of course, standing positions are the easiest to draw.
[I still cheat my way out of it and simply draw them standing there most of the time too. xD]
As for drawing hands, start off a sheet and just sketch a page full of hands. That's what I do. Experiment with drawing fingers, thin fingers, chubby fingers, boney fingers. Then start experimenting positions. An opened hand, a closed one and stuff like that.
It's always best to look at how other people draw their hands. Look at your favorite manga or pictures and observe closely how the hands are shaped and drawn. Then try if you can do something similar and make it into your own style. =D