In Orwell's "Politics and the English Language," he lays out six rules for good writing, which to him is clear, precise writing that tells the truth. Anyone who has taken a writing course will find them familiar, as they are foundational rules explained in any book about good writing.
These rules are as follows.
i. Never use a metaphor, simile or other figure of speech which you are used to seeing in print.
In other words, Orwell says, don't use clichés. Don't simply repeat what everyone else is saying. Use fresh language that comes from your own mind. Clichés can become dangerous, he says, because they are stale and keep people from thinking for themselves.
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.
Rules 2 and 3 are fairly self-explanatory: Orwell advises prioritizing short words and concise language.
iv. Never use the passive where you can use the active.
The passive voice emphasizes the subject of a sentence: an example would be if someone wrote, "It is believed by many that ..." instead of "Many believe that ..."
v. Never use a foreign phrase, a scientific word or a jargon word if you can think of an everyday English equivalent.
Orwell condemns the many foreign words and phrases that have been introduced into English, arguing that a writer would be better off finding an equivalent English word than using terms such as deus ex machina or mutatis mutandis.
vi. Break any of these rules sooner than say anything outright barbarous.
Rules, Orwell implies, are meant to be broken. Orwell would much rather see a writer break one of these rules than write something "barbarous" and keep all of them.