This is from his essay Politics and the English Language http://www.george-orwell.org/Politics_and_the_English_Language/0.html
(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 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,
but one could not write the kind of stuff that I quoted in these five
specimens at the beginning of this article.
(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 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,
but one could not write the kind of stuff that I quoted in these five
specimens at the beginning of this article.
Here is one of those examples from earlier in essay:
I returned, and saw under the sun, that the race is not to the swift, nor
the battle to the strong, neither yet bread to the wise, nor yet riches
to men of understanding, nor yet favor to men of skill; but time and
chance happeneth
Here it is in modern English:
Objective consideration of contemporary phenomena compels the conclusion
that success or failure in competitive activities exhibits no tendency to
be commensurate with innate capacity, but that a considerable element of
the unpredictable must invariably be taken into account.