What are you saying (without actually saying it)? Here's an overview of some common body language, organized by body area.
Head and Face
We all know what a smile means; frowns are a bit more complicated, but generally we get those, too. At least we get, understand, what the person wants us to understand â one can fake frowns and smiles. How do you get past plastered faces?
Answer: the eyes. From Christ ("The light of the body is in the eye...") to Santa Claus ("His eyes â how they twinkled!"), we've gaged how people really feel by their eyes.
Watch out for how fast you blink, too. Studies suggest that people blink faster when they're nervous (Tesse 1996).
Of course, expressions are usually much more complicated. For more information, see Malcolm Gladwell's The Naked Face and Paul Ekman's book Emotions Revealed.
Oh, and don't forget appropriate eye contact! Don't stare, but don't look down or be away too often. You'll appear afraid or shifty.
Neck, Chest, and Back
Legs (When Sitting)
For more body language information, I recommend Using Body Language at ChangingMinds.org
Remember, none of these signals indicate the reason for the emotion, and none are foolproof. Emotions and body language occur in context. In the end, the most important thing isn't who you come across as, but who you actually are.