The basic principle of posing for a stills camera is...
Keep still and be natural.
Let me rephrase that...
Stay where you are told to,
and feel normal.
Let's break that down into two parts.
There are 2 videos below.
One talks about the lens used for headshots - the telephoto lens,
and how to work in front of it.
The other talks about being normal and natural in front of the camera.
CLICK ON ONE TO PLAY IT
Stay in Focus... please!
Fear and Loathing of Headshots
Please forgive the rough and ready nature of these videos.
I really don't have the time to fuss about it!