“Do not put statements in the negative form.
And don’t start sentences with a conjunction.
If you reread your work, you will find on rereading that a great deal of repetition can be avoided by rereading and editing.
Never use a long word when a diminutive one will do.
Unqualified superlatives are the worst of all.
If any word is improper at the end of a sentence, a linking verb is.
Last, but not least, avoid cliches like the plague.”

(William Safire, ‘Great Rules of Writing’)

This one makes me smile, as it’s meant to, though it has plenty of truth as well.