So, everyone always hears about how to pose, how to do expressions, how to move, and "smile with your eyes" has been around for a while. In fact, Peter Hurley did a video about it (which is long and I didn't make though most of it) - http://www.youtube.com/watch?v=ff7nltdBCHs - and a friend of mine commented on the video and the Model Mayhem thread "that must be a joke". I'm not going that far, as learning new expressions has advantages and it's own merits.
I get asked all kinds of stuff about expressions like that along with what to wear and all that sort of stuff. Thing of it is, I don't really have the answer, and doing odd (for you) expressions can and do look uncomfortable to a viewer. You don't want to walk into a interview for a job and have a half finished draft resume, likewise you wouldn't want to walk into a casting or meeting with a headshot that looks uncomfortable and forced.
My best advice to those getting headshots is to practice, learn how you want to present yourself, and look though your market and try to figure out what the person looking at your headshot wants to see. So if you're a model, are you going to do more commercial (as in everywhere but NYC and LA just about) or are you going for more of a fashion look. As a actor do you want more of a serious image, dark, light, funny, what do you think would fit into the roles you want to play? For a business person, what do your clients and consumers want to see, someone in a suit or more of a casual look?
I can help and give advice, believe me I can, but in the end it's really all about how you want to present yourself, who your viewer is, and what the market is like, and again, how you want to approach it. I can give direction, but the majority of choices are up to you and I'm here to help you get the best results you can.
Andrew Thomas Evans