Cliff notes from a wrting class:

                   William Safire's Rules for Writers
       Remember to never split an infinitive.  The passive voice should
never be used.  Do not put statements in the negative form.  Verbs 
have to agree with their subject.  Proofread carefully to see if you 
words out.  If you reread your work, you can find on rereading a great 
deal of repetition can be avoided by rereading and editing.  A writer 
must not shift your point of view.  And don't start a sentence with a 
conjunction.  (Remember, too, a preposition is a terrible word to end 
a sentence with.)  Don't overuse exclamation marks!!  Place pronouns 
as close as possible, especially in long sentences, as of 10 or more 
words, to their antecedents.  Writing carefully, dangling participles 
must be avoided.  If any word is improper at the end of a sentence, a 
linking verb is.  Take the bull by the hand and avoid mixing 
metaphors.  Avoid trendy locutions that sound flaky.  Everyone should 
be careful to use a singular pronoun with singular nouns in their 
writing.  Always pick on the correct idiom.  The adverb always follows 
the verb.  Last but not least, avoid cliches like the plague; seek 
viable alternatives instead.