Oh man, perspective is such a pain, particularly where the human body is concerned. That is my achilles heel and my only response has been to just draw it over and over until I get it right... one time I had my little sister pose for me so that I have something to draw reference from when I tweak it in Photoshop. Generally I draw the pose first in what I call "rag doll sketches" which is basically the character in the most basic shapes I can get (squares, triangles, circles, pentagons, etc) and just keep twisting it until I have something that I'm satisfied with.