1. Dialogue should be brief.
2. It should add to the reader’s present knowledge.
3. It should eliminate the routine exchanges of ordinary conversation.
4. It should convey a sense of spontaneity but eliminate the repetitiveness of real talk.
5. It should keep the story moving forward.
6. It should be revelatory of the speaker’s character, both directly and indirectly.
7. It should show the relationships among people.
Good points; I’ve always thought: it should add to the plot of the story, never have dialogue just for the sake of dialogue (how real people talk in real life).