Talking About Dialogue

I''m currently reading Reading Like a Writer by Francine Prose.  One exercise that Prose gives her students in one of her English classes is to listen to a conversation between two people.  Prose says that when people speak to each other their conversations have many goals.  She writes about a man and woman having a conversation and noted that the woman was romantically interested in the man she's talking to but to Prose it was clear that the man was gay.

Conversations have many goals at one time.  A simple invitation to lunch with a friend may really be about getting information as well as having a meal.  So why don't you give this exercise a try.  I think it'll be worth while.  Find two people having a conversation and write about the conversation and see what you discover about the way people talk to each other.