From 'Politics & the English Language' by George Orwell

Good writing is for all time. Good, clear writing is rare. Good writers advising on how to write clearly are rarer still.

But one can often be in doubt about the effect of a word or a phrase, and one needs rules that one can rely on when instinct fails. I think the following rules will cover most cases:

(i) Never use a metaphor, simile, or other figure of speech which you are used to seeing in print.

(ii) Never us 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.

These rules sound elementary, and so they are, but they demand a deep change of attitude in anyone who has grown used to writing in the style now fashionable. One could keep all of them and still write bad English...

Politics & the English Language, 1946. Full text here.