Firstly, relax your facial espression and body but leave your eyes deliver the message(strong,sexy,confused,dull,naive,aggressive...)
And you need to always exaggerate your pose. Make sure you show those angle, curve, length.
But always make sure you look "not struggling"for the pose. Beautiful long neck is essential to make you look as elegant as a swan, don't pose like a turtle.

The last but not the least: Be Confident!
Written by model CC Wang
http://www.chuchiaowang.com/
