1. Avoid alliteration. Always.
2. Prepositions are not words to end sentences with.
3. Avoid cliches like the plague. (They're old hat.)
4. Employ the vernacular.
5. Eschew ampersands & abbreviations, etc.
6. Parenthetical remarks (however relevant) are unnecessary.
7. It is wrong to ever split an infinitive.
8. Contractions aren't necessary.
9. Foreign words and phrases are not apropos.
10. One should never generalize.
11. Eliminate quotations. As Ralph Waldo Emerson said, "I hate quotations. Tell me what you know."
12. Comparisons are as bad as cliches.
13. Don't be redundant; don't use more words than necessary; it's highly superfluous.
14. Be more or less specific.
15. Understatement is always best.
16. One-word sentences? Eliminate. Cease. Desist.
17. Analogies in writing are like feathers on a snake.
18. The passive voice is to be avoided.
19. Go around the barn at high noon to avoid colloquialisms.
20. Even if a mixed metaphor sings, it should be derailed.
21. Who needs rhetorical questions?
22. Exaggeration is a billion times worse than understatement.
Never use a big word when a diminutive one will suffice.
Orwell's Rules, By Which Xena Lives:
1. Never use a metaphor, simile or other figure of speech which you are used to seeing in print.
2. Never use a long word where a short one will do.
3. If it is possible to cut a word out, always cut it out.
4. Never use the passive where you can use the active.
5. Never use a foreign phrase, a scientific word or a jargon word if you can think of an everyday English equivalent.
6. Break any of these rules sooner than say anything outright barbarous.
Perhaps the best book ever written on how to write clear, concise, and gramatically correct prose is Elements of Style, by William Strunk and E.B White (and no, I'm not trying to talk Ebonics). The book is only 85 pages or so and covers just about everything you just said and a little bit more. A copy sits behind my desk and I assign it as mandatory reading to all new employees.