1. Sociopaths typically don't smalltalk about themselves as much as normal people do. They will direct the conversation back to the new acquaintance as much as they can.
2. A sociopath will reveal "personal" details about himself strategically, i.e. for the purposes of misdirection or a false sense of intimacy/trust. Revelations of actual truths are very rare and may be perceived as a small slip of the mask.
3. Sociopaths frequently hesitate before responding. It will be unclear to you whether they are bored, annoyed, lying, or all three.
4. No strong reactions to illogical hotbed political/social topics (e.g. Octomom or Catholic priest child molestation).
5. Monotone voice (I am told).
6. A tendency to take things too literally or otherwise not respond appropriately to small emotional cues.
7. Cold indifference to one or more family members.
8. Seemingly a different person when "distracted."
9. Disconnect between what the sociopath says and does, e.g. seems charitable but does not give money to homeless or vice versa.
10. Never shows signs of embarrassment. Easily wins over large crowds with confidence. "Poise" in this case = lack of nerves.
11. Does not fit stereotypes for gender, race, ethnicity, religion, age, sexual orientation, or career. Could seem foreign, bisexual, older or younger, pious, wealthy or poor, but may also just seem unplaceable.
12. Can flip flop between keeping a very low profile (the observer) to being the life of the party (the actor).I don't think all of these would apply to all sociopaths, and certainly many of them apply to people who aren't sociopaths, however they all have the advantage of being directly observable by a layperson, at least without the aid of a brain scan or 10 page questionnaire. Also, because they're seemingly inconsequential and not directly related to the classic sociopath/antisocial traits, a sociopath would have less reason to mask them.
Do some of these seem particularly predictive or not? Any other suggestions?