David Deangelos Double your dating videos on body language coverd posture well.
Also pick up 101 body language covered it well.
some pointers
1. shoulders back
2. chest out
3. buttocks and back tight
4. move naturally and flowing, walk a little slower than everyone else ( also make sure both your feet point foward this is a particular problem for me I kind of woddle)!
5. dont be afraid to take up space!
I also like head tilted to the side and pointed upward.
As far as facial expressions think James Dean, Beneico Del Torro
Brow furrowed, lips pursed
http://www.youtube.com/watch?v=qFkbVYeKHF0