George Orwell’s six elementary rules (“Politics and the English Language”, 1946):
- Never use a Metaphor, simile or other figure of speech which you are used to seeing in print.
- Never use a long word where a short one will do.
- If it is possible to cut out a word, always cut it out.
- Never use the Passive where you can use the active.
- Never use a foreign phrase, a scientific word or a Jargon word if you can think of an everyday English equivalent.
- Break any of these rules sooner than say anything outright barbarous.
This is on the economist.com styleguide.