The episodes of a tale shall be necessary parts of the tale, and shall help to develop it.
The personages in 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.
The personages of the tale, both dead and alive, shall exhibit sufficient excuse for being there.
When the personages of a tale deal in conversation, the talk shall sound like human talk, and be 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 neighbourhood of the subject in hand, and be interesting to the reader, and help out the tale, and stop when the people cannot think of anything more to say.
When the author describes the character of a personage in his tale, the conduct and conversation of that personage shall justify said description.
When a personage talks like an uneducated loser, he shall not act like an Oxford graduate.
Crass stupidities shall not be played upon the reader by either the author or the people in the tale.
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.
The author shall make the reader feel a deep interest in the personages of his tale and in their fate; and that he shall make the reader love the good people and hate the bad ones.
The characters in a tale should be so clearly defined that the reader can tell beforehand what each will do in a given emergency.
A tale can be interesting, the characters believable - but the reader won't read enough of it to find out if the language of the story is awkward or unclear. To prevent this, Twain's Rules require that the author shall: SAY what he is proposing to say, not merely come near. USE the right word, not its second cousin. Eschew surplus matters. NOT omit necessary details. AVOID slovenliness of form. USE good grammar. EMPLOY a simple, straightforward style.