You send out messages all the time and communicate with others without even speaking! The non-verbal cues you make convey all sorts of information to others about you. For example, avoiding eye contact conveys extreme shyness, and/or a complete lack of trust in others.
Folding your arms is a defensive posture (unless you’re cold) which alerts others that you may be angry, or just don’t trust them.
Keeping your hands in your pockets and playing with change indicates miserliness (being cheap.) Twirling hair in your fingers absent-mindedly sends a message that you lack professionalism or get bored easily. All of these non-verbal cues send out messages to others and can sabotage your attempt to make a positive first impression.
For example, repeated face touching (esp. your nose) indicates deception. Repeatedly checking your watch indicates extreme boredom and rudeness! Good posture is a sign of confidence and leaning in towards others as they speak conveys interest. Following are informative web sites you can reference, for advice on how to control your body language and convey the most professional demeanor: