If it's a superficial analysis (ie interview), then punctuality, dress and preparation on their part (investigation prior to the meeting) is valid. If they haven't inquired about the dress code, then they should assume it's formal. If you have a minute to do a slightly deeper analysis then Google is your friend: how do they present themselves on social networks, do they have a blog, have they commented in forums (do they troll) have they posted code (usually a goldmine). If the profession is technological and they have no web presence whatsoever, that's usually a red flag in itself.