Perhaps the best thing ever written about writing.

The full version:

http://www.orwell.ru/library/essays/politics/english/e_polit


The 6 main points (for those who think they don't have time to read):

1. Never use a metaphor, simile, or other figure of speech which you are used to seeing in print.
   
2. Never use a long word where a short one will do.
3. If it is possible to cut a word out, always cut it out.
4. Never use the passive where you can use the active.
5. Never use a foreign phrase, a scientific word, or a jargon word if you can think of an everyday English equivalent.
6. Break any of these rules sooner than say anything outright barbarous.