A writer must not shift your point of view. If the writer is considerate of the reader, he won't have a problem with ambiguous sentences. Don't write a run-on sentence its hard to read you must punctuate it. If a dependent clause precedes an independent clause put a comma after the dependent clause. But avoid commas, that are not necessary, and don't overuse exclamation marks!!! Use the semicolon properly, always use it where it is appropriate; and never where it isn't. Reserve the apostrophe for it's proper use and omit it when its not needed. In statements involving two word phrases, make an all out effort to use hyphens, but make sure you hyp- henate properly.
Take the bull by the hand and avoid mixing metaphors. Always pick on the correct idiom. Avoid colloquial stuff, and trendy locutions that sound flaky. Also, avoid all awkward or affected alliteration. Unqualified superlatives are the worst of all. Beware of and eschew pompous prolixity, and avoid the utilization of enlarged words when shortened ones will do. Avoidification of neologisms strengthenifies your prosification. Avoid using sesquipedalian words. It is not resultful to transform one part of speech into another by prefixing, suffixing, or other alterings. Perform a functional iterative analysis on your work to root out third generation transitional buzz words. Steer clear of incorrect forms of verbs that have snuck into the language. The de facto use of foreign phrases vis-a-vis plain English in your written tete-a-tetes makes the sentence harder to understand.
Everyone should be careful to use a singular pronoun with singular nouns in their writing. 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. Write all adverbial forms correct. Verbs has to agree with their subjects, and the adverb always follows the verb. This sentence no verb. Which is not a complete sentence, but merely a subordinate clause. A preposition is something you should never end a sentence with. And don't start a sentence with a conjunction.
Last but not least, avoid dyed-in-the-wool cliches like the plague; seek viable alternatives.
(Most of this text is from William Safire, Fumblerules: A Lighthearted Guide to Grammar and Good Usage , New York Times, November 4, 1979; later also published in book form.)