The one thing that will really bring your drawings to life is the 'line of action' or the imaginary line that dictates how the body will move. You can also think of it as the back bone of a character. This line should always be used in setting up a pose, as you can see in the pic I posted, I get a wide range of emotions with no faces using only their bodies. When all else fails, get up and see how your body bends and shapes when trying to act out emotions. Think to yourself, "how would I be if I just hit a dog with my bike?" or, 'What are different ways I can clap?"
I think the one thing I see the most with people learning to draw is they jump into the details too quickly. They want to get the facial expression and details of the face before establishing the body. I suggest doing what I have done and fill up some pages of thumbnail sketches portraying as many expressions as possible. The body language should always come first, the face just backs it up."
This is some very useful advice I found online recently when looking at some body language sketching.
Here are some of the pictures I have tried to sketch emotion just through the body language...
Video upload of the day