Since we're talking about fan fic... okay, we're not. But if we were...
Whilst wandering merry as a cloud around the Internets the other day, I came across a website about writing marginally readable fan fiction, by the amusingly named Ms. Nitpicker. Since I totally flatter myself that I write more than marginally readable fan fiction, I of course decided to look at it and then pat myself on the back for already instinctively following all the rules of Really Good Fan Fic Writing.