Today I went back to posemaniacs.com ; one thing I can always recommend doing is to do the 30 second drawings they have. Because even if you think you're good, doing those exercises loosens you up. You are forced to think fast so you get more efficient with your line usage and your shapes and lines become loose and fluid. Well, it's only the first time I did them again for a while, so hopefully I'll get better again :)
I started with 60 second poses and then went to 30 second:
I then went on to some chest studies...it's so difficult to get that feeling for natural weight.
After those I went back to some more posemaniacs (45 seconds)