Always avoid all aimless alliteration.
Prepositions are not words to end sentences with.
And don’t start a sentence with a conjunction.
Parenthetical remarks are unnecessary (even when relevant).
It’s wrong to ever split an infinitive.
Contractions shouldn’t be used.
Avoid ampersands & abbreviations, etc.
Foreign phrases apropos of writing are not de rigueur.
One should never generalise.
Eliminate quotations. As Ralph Waldo Emerson said: “I hate quotations. Tell me what you know.”
Comparisons are as bad as cliches.
Be more or less specific.
One-word sentences? Eliminate.
Exaggeration is a million times worse than understatement.
Analogies in writing are like feathers on a snake.
The passive voice is to be avoided.
Move heaven and earth to avoid colloquialisms.
Even if a mixed metaphor lights up and calls out to you, it should be derailed.
Who needs rhetorical questions?
Don’t use commas, that, are not necessary.
Never use a big word when a diminutive alternative would suffice.
inaccurate Capitalisation Is conFusing.
Subject and verb always has to agree.
Steer clear of any incorrect verb forms that have snuck into the language.
It is behoven upon us to avoid archaic expressions. Avoid archaeic olde spellings too.
Don’t overuse exclamation marks!!!
Placing a comma between subject and predicate, is not correct.
Avoid un-necessary hyphenation.
Poofread your work carefully to ensure you haven’t out letters or words.
Don’t repeat yourself, or say again what you have said before, thus avoiding repetition.
Avoid run-on sentences they can be hard to follow.
Eschew pedantic obfuscation.
Don’t use hyperbole. Not one in a million can do it effectively.
Use the apostrophe in it’s proper place, and omit it when its not needed.
Don’t use no double negatives.
Use your words correctly, irregardless of how others use them.
Don’t indulge in sesquipedalian lexicological constructions.
Last but not least, avoid cliches like the plague. They’re old hat.
With credit to Bink286 on Motley Fool Jokers Corner and others