First Impression

Your first impression matters. A lot.
Your first impression is when a stranger meets you, greets you, and finally, judges you. Judge the way you look, act, talk, the way you smile. In fact, I think that a stranger's judgement on your physical appearance is the most accurate one because they are unbiased about your character. Personality, not so much.
Psychology Today's article "First Impression" gives scientific insight on the effects of that first encounter, claiming that "that snapshot captures important elements of the truth." This snippet of the article leads into the analysis of our weaving of first impressions:

The answer lies in part in how the brain takes first-impression Polaroids—creating a composite of all the signals given off by a new experience. Psychologists agree that snap judgments are a holistic phenomenon in which clues (mellifluous voice, Rolex watch, soggy handshake, hunched shoulders) hit us all at once and form an impression larger than their sum. 

So, whether it's an interview or a blind date, just make sure you're giving an impression you won't regret. After all, you don't want to give them the wrong one.