* The Rule of Plans: If the characters explain The Plan to the reader beforehand, it cannot work. This is because no author wants to describe the same thing twice and if it worked, acting it out would be just like explaining it.
The Corollary of Detailed Plans: If the characters explain the Plan in detail, it will go horribly, horribly wrong. The description of the Plan is only there to serve as a blueprint of how it went wrong.
The Rule of Significant Characters: Any character important in the second half of a story must be introduced in the first half. This is to prove you're not just making it up as you go along. Writers who are just making it up as they go along are advised to introduce a lot of extraneous characters in the first half just in case you need them later.
The Corollary of Secret Identities: Characters whose specific identity is unknown but who appear throughout the story as an actor (eg, a masked thief) must be mentioned by their secret identity at least once in the first half of the story and be revealed as such in the second half. This applies even if their real name is irrelevant and your story is not about the mystery of unmasking them.
The Rule of Resolutions: Any special abilities/skills/super powers/vulnerabilities which will be critical at the climax must be mentioned well before the climax. This is also to prove that you aren't just making it up as you go along. Writers who are just making it up as they go along should be aware that introducing extraneous powers well before the climax in case you need them later doesn't work as well as doing the same thing with characters.
What other narrative conventions can you think of? When have you seen these conventions flouted -- especially flouted effectively? The best case of flouting that I know is on the Corollary of Secret Identities in Alan Moore's "V for Vendetta": V is never unmasked and it doesn't matter who he "really" was, or if he was anyone that appeared elsewhere in the graphic novel.
Or, almost as good: followed but followed badly? I remember two instances of bad implementations of the Corollary of Secret Identities: one where the author clearly had one character in mind for the "real villain", and then decided that was too obvious and switched it to a different character, who made no sense at all as the secret id. And another where the secret id was completely irrelevant to the story, but had still been mentioned in a single throwaway paragraph near the start just to satisfy narrative convention.