looking over the thread i agree with wht everyone else has said mostly :) your'e progressing really well, and i like the badass-ness your drawings often seem to portray :) something else i wanted to suggest was getting a feel for the way the human body flows. whenever you can, just doodle little stick figures that follow the flow of the human body. once you get that flow, everything else gets a little easier
you don't have to make them as complex as this, but see how the bones curve? that's what people are really like. you can simplfy the shoulders and hips with a line, but following the curve of the spine and the other limbs will really improve the human-ness of you drawings. the body tends to follow a line, caled the line of action
the pink line represents the line of action and learning this rule helps to make the body seem more organic and alive.
hope this helps :)