Prepositions are not words to end sentences with.
And don't start a sentence with a conjunction.
It is wrong to ever split an infinitive.
Avoid cliches like the plague. (They're old hat.)
Also, always avoid annoying alliteration.
Be more or less specific.
Parenthetical remarks (however relevant) are (usually) unnecessary.
Also too, never, ever use repetitive redundancies.
No sentence fragments.
Contractions aren't necessary and shouldn't be used.
Foreign words and phrases are not apropos.
Do not be redundant; do not use more words than necessary; it's highly superfluous.