Rules and rules and rules, loads of them - from writers and about writing fiction. There's what looks to me like a lot of wisdom there (but then what do I know about it?), as well as much that you can ignore. There'd have to be plenty to ignore because if you tried to follow all these rules you might go crazy, or you might just end up writing something incomprehensible.
I like this one from Elmore Leonard: 'Avoid prologues: they can be annoying, especially a prologue following an introduction that comes after a foreword.' Yes indeed. You want to start straight in on the story, not fossick about with preliminaries, especially when you don't get to know what these are really saying till you're some way further into the book. Colm Tóibín is a hard taskmaster. 'No going to London', he says. 'No going anywhere else either.'
Then there is also this, from William Shakespeare's 10 rules: 'Write ye not a new tale if't can at all be helped. Plunder thou yon histories, myths and pre-Renaissance Italian romances for plot, setting, character, structure, style and theme. If anyone notice, claim ye homage.'