Nonverbal communication plays such an integral part

Nonverbal communication plays such an integral part of our lives and relationships, both professional and personal. But you are right to highlight that it both positives and negatives. Let's say you were giving a training on nonverbal communication; what two key points do you think every person should know about nonverbal communication? What tips do you think would most help folks when they find themselves unsure of how to read nonverbal communication?