I agree not everyone does everything the same exact and just like in Statistics there's variation.You shouldn't concern yourself with how "normal" people would react to the situation (who decides whose normal anyway) just go with what you feel. For example in that first situation, if you actually had a genuine interest in that girl, indicate it by doing something like smiling, touching her arm etc. Dave gave some pretty good situations on how to flirt.
What I'm wondering about is you mentioned "smiling, touching her arm etc", the girl on Yahoo!Answers mentioned touching on the arm as a way to flirt to see how she responds, and Dave said flirting is like a dance. They all have similarities in the big picture. What if men with normal social skills do things like this without even knowing about it? So I'm very curious about that and it's why I wonder what other men here think they would do if a woman leaned forward like that, smiled, and asked that question.