Harvard researcher, Amy Cuddy, researched first impressions and how you want to engage in every interaction with warmth and competence, leading with warmth first. This is because although our society has evolved a lot over the past thousands of years, our brains have not. So when we encounter someone new, our survival instincts ask whether this person is a threat? (warmth), and if so, could they enact on it? (competence).

The fastest way to exude warmth and competence in an interaction?

Smile (warmth) and have good posture (competence).

Notice, this is all before you've said a word.