Body language is a subject that only seducers, businessmen, and women seem to understand. The average man doesn't realise that 70% of communication is body language.
In today's society it is fundamental to success, to understand the principles of body language. Reading people is an art, therefore it can be learnt and perfected.
The arms are a powerful indication of a person's emotional state. Having the arms folded suggests a defensive persona. When you see a person fold their arms, it's a signal to be more softer around the person.
Open arms suggest a friendly and confident personality. Confident people tend to be more comfortable with their arms open, whilst using lots of hand gestures.
Facial Expressions are the main signal when determining a person's emotional state. Smiling is often a happy and friendly sign. However, not all smiles are genuine (As can be seen by the Joker in the Batman films). On a serious note, smiles are only genuine when creases appear in both the cheeks and eyes simultaneously.
Eye contact is by far the most effective use of non-verbal communication. Those who claim to have experienced "Love at first sight", owe that claim to making eye contact. The eyes are very powerful, and women use eye contact the best. When a woman catches your eye, in that split second she causes attraction within you, and so you begin to be seduced.
Your feet and legs also speak volumes. Generally, a man's feet are width apart, for obvious 'biological' reasons; and a woman's feet are always together. However, when a man's feet are far apart, that displays a dominant male characteristic. The same applies for a woman whose feet are far apart.