this tutorial is pretty basic, but it hits on a lot of good posing information. http://cherazor.deviantart.com/art/G...play-172433587
facial expressions are a little tougher because they look different on different people. like it's much easier for me to look sad and serene than happy or angry just because i have a round face with deep set eyes. some people look silly doing the opposite and vice versa. im sure with a little practice you can master all the emotions. definitely practice in the mirror, it gives you a great idea of what you look like in pictures. practice makes perfect
not that i'm an expert or anything, i've been cosplaying for many years and just picked some stuff up along the way :3 good luck!