Found on the internet.

1. Avoid alliteration always.
2. Prepositions are not words to end sentences with.
3. The passive voice is to be avoided.
4. Avoid cliches like the plague. They’re old hat.
5. It is wrong to ever split an infinitive.
6. Writers should never generalize.
Seven: Be consistent.
8. Don’t use more words than necessary. It’s highly superfluous.
9. Be more or less specific.
10. Exaggeration is a billion times worse than understatement.

More tips at PlainLanguage.gov