1. If someone says "Oh wow" or "That's awesome" more than once during a conversation, they're done.
  2. If someone's text responses are continuously a quarter the length of your texts, they're done.
  3. "You're the best" means "I don't love you but you're nice so I feel bad saying it."
  4. If someone tells you they wish they could hang out but it's a super crazy week/month/year, they're done.
  5. "Ha." means, "I'm acknowledging you made a joke. I don't find it or you funny. Move along."
  6. No one enjoying a conversation ever needs to excuse themselves to get another drink without offering to bring you one, too.
  7. "Oh cool. My boyfriend/girlfriend/wife/husband likes that, too" = no sex for you.
  8. If someone says "interesting, interesting" they are, in truth, decidedly uninterested
    Suggested by @ChrisK
  9. "I think you're amazing" = they're about to break up with you
    Suggested by @allyhord