The rules presented here are by Mark Twain as enumerated in "Fenimore Cooper's Literary Offenses" and I include them for your enjoyment and edification.

Mark Twain's Rules of Literary Art

The rules governing literary art in the domain of romantic fiction require:

  1. That a tale shall accomplish something and arrive somewhere.
  2. They require that the episodes of a tale shall be necessary parts of the tale and shall help to develop it.
  3. They require that the personages of a tale shall be alive, except in the case of corpses, and that always the reader shall be able to tell the corpses from the others.
  4. They require that the personages in a tale, both dead and alive, shall exhibit sufficient excuse for being there.
  5. They require that when personages of a tale deal in conversation, the talk shall sound like human talk, and be talk such as human beings would be likely to talk in the given circumstances, and have a discoverable meaning, also a discoverable purpose, and a show of relevancy, and remain in the neighborhood of the subject in hand, and be interesting to the reader, and help out the tale, and stop when people cannot think of anything more to say.
  6. They require that when the author describes the character of a personage in his tale, the conduct and conversation of that personage shall justify said description.
  7. They require that when a personage talks like an illustrated, gilt-edged, tree-calf, hand tooled, seven dollar Friendship's Offering in the beginning of a paragraph, he shall not talk like a negro minstrel in the end of it.
  8. They require that crass stupidities shall not be played upon the reader as "the craft of the woodsman, the delicate art of the forest" by either the author or the people in the tale.
  9. They require that the personages of a tale shall confine themselves to possibilities and let miracles alone; or, if they venture a miracle, the author must so plausibly set it forth as to make it look possible and reasonable.
  10. They require that the author shall make the reader feel a deep interest in the personages in his tale and in their fate; and that he shall make the reader love the good people in the tale and hate the bad ones.
  11. They require that the characters in a tale shall be so clearly defined that the reader can tell beforehand what each will do in a given emergency.
    In addition to the large rules there are some little ones. These require that the author shall:
  12. Say what he is proposing to say, not merely come near it.
  13. Use the right word, not its second cousin.
  14. Eschew surplusage.
  15. Not omit necessary details.
  16. Avoid slovenliness of form.
  17. Use good grammar.
  18. Employ a simple and straightforward style.

I highly recommend that you read the essay in its entirety. It's one of the funniest pieces of literary criticism ever written. And might help keep you from some literary offences.

Fenimore Cooper's Literary Offenses on Project Gutenburg

Here are a few extra words of advice on writing from Twain, still just as good today as they were then:

I notice that you use plain, simple language, short words and brief sentences. That is the way to write English - it is the modern way and the best way. Stick to it; don't let fluff and flowers and verbosity creep in. When you catch an adjective, kill it. No, I don't mean utterly, but kill most of them - then the rest will be valuable. They weaken when they are close together. They give strength when they are wide apart. An adjective habit, or a wordy, diffuse, flowery habit, once fastened upon a person, is as hard to get rid of as any other vice. - Letter to D. W. Bowser, 20 March 1880

The difference between the almost right word & the right word is really a large matter--it's the difference between the lightning bug and the lightning. - Letter to George Bainton, 10/15/1888

Fiction is obliged to stick to possibilities. Truth isn't.