• Remember to never split an infinitive.
• The passive voice should never be used.
• We should not make spelling misteaks in writing.
• Avoid run-on sentences they are hard to read.
• Don't use no double negatives.
• Use the semicolon properly, always use it where it is appropriate; and never where it isn't.
• Reserve the apostrophe for it's proper use and omit it when its not needed.
• Do not put statements in the negative form.
• Verbs has to agree with their subjects.
• No sentence fragments.
• Proofread carefully to see if you any words out.
• Avoid commas, that are not necessary.
• If you reread your work, you will find on rereading that a great deal of repetition can be avoided by rereading and editing.
• A writer must not shift your point of view.
• Eschew dialect, irregardless.
• And don't start a sentence with a conjunction.
• Don't overuse exclamation marks!!!
• Place pronouns as close as possible, especially in long sentences, as of 10 or more words, to their antecedents.
• Hyphenate between syllables and avoid un-necessary hyphens.
• Write all adverbial forms correct.
• Don’t use contractions in formal writing.
• Writing carefully, dangling participles must be avoided.
• It is incumbent on us to avoid archaisms.
• If any word is improper at the end of a sentence, a linking verb is.
• Steer clear of incorrect forms of verbs that have snuck in the language.
• Take the bull by the hand and avoid mixed metaphors.
• Avoid trendy locutions that sound flaky.
• Never, ever use repetitive redundancies.
• Everyone should be careful to use a singular pronoun with singular nouns in their writing.
• If I've told you once, I've told you a thousand times, resist hyperbole.
• Also, avoid awkward or affected alliteration.
• Don't string too many prepositional phrases together unless you are walking thorugh the valley of the shadow of death.
• Always pick on the correct idiom.
• "Avoid overuse of 'quotation "marks."'"
• The adverb always follows the verb.
• Last but not least, avoid clichés like the plague; seek viable alternatives.

Adapted from "On Language"  The New York Times, November 4, 1979 by William Safire