When two people interact, their voices, facial expressions and mannerisms synchronize. The emotions are literally "contagious" and spread from one person to another.
Your job as a seducer is to spread the right kind of energy. Relaxed, playful and at ease with yourself.
Spread the wrong kind of energy and its over before it begins.
An interesting book on the subject is Malcom Gladwell's "The Tipping Point". It's a fascinating book and explains many concepts related to seduction. Give it a look.