I try to look periodically at Orwell's “Politics and the English Language” and I've shared it with many colleagues over the years. I used to have a small card with the basic rules taped to my desk, but I know them by heart now:
(i) Never use a metaphor, simile, or other figure of speech which you are used to seeing in print.
(ii) Never use a long word where a short one will do.
(iii) If it is possible to cut a word out, always cut it out.
(iv) Never use the passive where you can use the active.
(v) Never use a foreign phrase, a scientific word, or a jargon word if you can think of an everyday English equivalent.
(vi) Break any of these rules sooner than say anything outright barbarous.
Now the Economist's Johnson blog points out that the man himself used the passive voice in the selfsame essay, and that perhaps he might have been a little dictatorial in his blanket prohibitions. Moreover, the escape hatch provided by number 6 might be a little too small. The author suggests some edits:
i) Avoid using metaphors, similes, or other figures of speech which you are used to seeing in print. Think of fresh ones wherever you can.It sacrifices poetry for clarity, but it makes sense. Of course, it can always be improved.
(ii) Prefer short words to long ones.
(iii) Try cutting a lot of your word-count, especially those words that add little extra meaning.
(iv) Don’t over-use the passive voice. And whether passive or active, be clear who did what to whom.
(v) Prefer everyday English to foreign, scientific or jargon words.
(vi) Good writing is no place for the tyrant. Never say “never” and always avoid “always”, or at the least handle them with care. Overusing such words is an invitation for critics to hold you to your own impossible standard.