One thing you should not forget and which doesn't get enough attention from people I think, me included (just like shoulders) are hands and fingers. Make sure to check out these drawings and what Angus McLane has to say about it.
Another source I like to check for reference and inspiration (which is more of a hit & miss than checking out animation masters and their work, but still) are statues and maquettes.
I check out bigbadtoystore, cornerstorecomics and other sites, because I can't help myself, I'm a nerd. But every now and then you find a really cool statue. In this case, it's the Premium Format Figure of Star Wars' Asajj Ventress. I actually don't like the figure that much, but the photos of her hands were really cool.
It's expressive, strong, has a nice silhoutte (in this picture only though), it just ads to the figure (although the body pose could have been stronger).

The other picture shows her holding the lightsaber and it's a good example of how you should really push the poses of your hands and fingers as they hold something. Often I see the hammer pose, or worse, the broken wrist pose.

Try to to really think about how the wrist and fingers are working together in order to wrap around and hold on to an object, like this next photo:

It's tedius work, but pays off in a big way.
- pic source of hammer and Star Wars figure (c) 2008 Lucasfilm Ltd. & TM.
>>Click here to read the rest of the post...
>>Minimize the post by clicking here.