Understand your man: If you're talking about something serious with your man and he suddenly looks away or seems preoccupied, don't worry. He's probably not ignoring you. The gesture may indicate that he's paying attenttion but disagree with what you're saying and is concealing his opinion.
Connect with the kids: Wondering your teenager threw a wild house party while you were out of town? Ask him and watch if he brings his hand to his face or mouth, chances are there were two dozen kids hanging from the chandelier. A younger child will probably cover his entire mouth with his hand while formulating a fib.
Relate to a boss: She'll be more receptive to talking about that raise when she's in an open position--leaning forward in her chair, one foot slightly in front of the other, head up. Beware the "figure four leg clamp" (sitting with the ankle of one resting on the knee of the other, with both hands clenching the shin). This reveals an antagonistic attitude, and she may not be interested in hearing opinions that don't mirror her own.
Understand a woman: At the end of the date, you say "I'll call you a few days later" and she says "Tha't would be great" by raising her left hand in front of her face, then fluttering her fingers in what looks like a sexy little au revoir wave as she slowly backs away. What's her body language saying to you? You didn't notice that by backing away from you, by using her hand as a subtle barrier to keep you at bay, and by fanning the air with her "goodbye" message, her body contradicted every word her lips formed.
If her palms are open, it shows sincerity and receptivity - she isn't hiding anything from you.
Read your own Body language: Arms Folded / Legs Crossed. This can be seen as defensive or an end to the conversation. So have arms hang freely or hold a glass of water, a business card or note taking instruments while communicating with others. Be open with open arms. Note: If you need to cross legs, cross at your ankles and not your knees. Sitting tightly folded up says that you are closed to communications.