Write an exchange of dialogue between two (or more) characters, during which at least one character decides he/she has another “pegged” – as in, understands what kind of person they really are, what category they belong in, etc.  How do they treat the other person, and the conversation, afterward?  If you get on a roll with this part, go one step further and, still in dialogue, prove the character’s judgement about the other person wrong.  And then how does the conversation change?