- Don't use no double negatives.
- Eschew obfuscation.
- Never use a preposition to end a sentence with.
- The passive voice should never be employed.
- You should not use a big word when a diminutive would suffice.
- It is bad to carelessly split infinitives.
- About those sentence fragments.
- Avoid clichés like the plague.
(Just came across these on Advice to Writers, originally from William Safire.)