[I have borrowed, translated and adapted these tips from a French website. That explains the references to French authors, in case you were wondering. These tips are intended for use in writing for the web, but would be useful in many other types of writing as well.]
1. Thou shalt write short sentences.
You are not Proust! So do not write sentences of more than one or two lines. If you hesitate between several constructions, always choose the one with the fewest words. Your texts will be more rhythmic.
Tip: exchange semicolons for periods.
2. Thou shalt limit thyself to subject, verb and object.
The subject + verb + object scheme is the simplest grammatically. It is instantly recognizable and understandable to the reader. So avoid complex grammatical constructions, subordinate clauses, interpolations and parentheses within the same sentence.
Tip: turn most subordinate clauses into independent sentences.
3. Thou shalt write one idea per sentence.
One idea per sentence, one point per paragraph, one subject per article. Don’t try to say everything at once, at the risk of drowning your reader. Prioritize your ideas and start with the most important.
Tip: If your article is too long, divide it into several articles grouped by folder or series.
4. Thou shalt simplify thy vocabulary.
You do not write to amuse yourself but to make yourself understood. Don’t try to dazzle your readers with exotic words or literary style. Favour simple words known to all.
Tip: use only words that you know how to spell.
5. Thous shalt translate jargon.
You don’t need to eliminate all trade or professional jargon, but ensure the first occurrence of such a word is translated into plain English, including all acronyms and words from other languages. Not only will your readers thank you, but it will be easier for search engines to find your page because you will broaden your semantic field.
Tip: imagine you are writing for your grandmother.
6. Thou shalt avoid negations.
It is forbidden to forbid! It is not always easy (as in this article which intends to be educational), but avoid negative terms as much as possible. Opt instead for positive constructions, more involving and more direct. Flee double negatives that need to be read twice to get the meaning.
Tip: always replace “do not hesitate to do this” with “do this”!
7. Thou shalt avoid the passive voice.
Better to write “The cat eats the mouse” than “the mouse is eaten by the cat.” Not only does the passive use more words than the active form (7 words against 5), but it is also more complex to analyse. Therefore reverse passive sentences, transforming the object into subject.
Tip: choose action verbs like create, produce, decide, etc.
8. Thou shalt avoid adjectives and adverbs.
“Journalists (…) who want to use an adjective come see me in my office. Those who will use an adverb will be shown out the door,”wrote Georges Clemenceau in a memo while he was editor of L’Aurore. Years have passed, the media have changed, but the counsel remains valid.
Tip: first remove all useless instances of “true” and “genuine” from your texts.
9. Thou shalt avoid the subjunctive.
Avoid the subjunctive: limit yourself to the indicative. Also avoid the tenses we learned at school like the pluperfect, future anterior, etc. Try to stick to the present, the past, the imperfect, the future and the imperative.
Tip: use the infinitive as much as possible.
10. Thou shalt read thy article out loud.
Proofread your text carefully before publishing it. Locate the long sentences, overly complex constructions, etc. Check that you have applied all the above rules.
Tip: re-read aloud to identify difficult to read sentences. Flaubert called it the gueuloir test, you will see, it works!
(I presume Gueuloir was Flaubert’s invention; it’s not found in any dictionary. Gueuler means to speak very loudly, to yell.)
If you read French, the original article is found at: http://editoile.fr/10-astuces-pour-ecrire-plus-simplement/
Flatlander Faith 
I like your article, but I slightly disagree with you.
I think these are good guidelines for writers like you and me probably (like was said, we don’t have Proust’s talent). However, I think there are different categories of writings and of writers, and different categories of readers.
By this I mean that what you wrote would apply more for people who have relatively little experience in writing, and/or who are trying to reach an audience that either has a low level of instruction, a low level of fluency in that given language, a low attention span or is just ignorant about that specific topic. Children would usually fall into this category. People for whom English is a second language also would (that is why Wikipedia has pages in English but also pages in Simple English, for foreigners who know little English but want to access the information since it is not available in their language).
People in general, and especially people who read a lot learn a lot a vocabulary from books. Actually, most of my knowledge and vocabulary comes from what I have read. Some estimates tell us that there are 600,000 words in English, but that to read newspapers, or listen to the news, if you know the 4,000 basic words of English, you can understand more than 95% of what is being said. The average person only uses 1,200 different words for conversation.
We know many more words than we use. Why is that? Because we have either read or heard them before. That means that someone else used them in speech or in writing, thereby enriching our vocabulary. We most probably won’t use that word, but from there on we will know what it means.
I think it is good to have a broad vocabulary. Studies tend to show that it really enhances a person’s ability to understand the world and think rationally if he knows a term to describe almost every situation in life. It definitely is an advantage (not in a spiritual sense but rather earthly) in speeches and in conversation, because it makes you appear more intelligent and intimidates others.
That is why native speakers of dominant languages (especially English today) have a great advantage over others in international conferences and meetings. If you look at who speaks the most in English Universities, English-speaking meetings in international business, and UN speeches, native English speakers take up much more room than what their numbers would suggest they should. They also get their way easier because they can speak in a wordy way to get their point across (sometimes some of it is above the foreigner’s head) and the non English-speaker first of all doesn’t want to admit that he didn’t understand everything, and secondly doesn’t have a sufficient word arsenal to oppose the English-speaker fairly. That is how you dominate the world. Some when my dad goes to Morocco or Lebanon to talk at a IT conference in French, he looks much smarter than the others because most of them can’t explain themselves in either Berber, Arabic or French (or English for that matter), because they never learned the “informatique” vocab in any of those languages.
I went to a conference on Wednesday where an Iranian brought a speech. He obviously knew a lot about micro-climatology, but his French was not up to par with his knowledge, and people laughed at him a few times because he stumbled on words such as “clairière” (clearing in the woods) and he wasn’t able to make it as entertaining as the other speakers, and I’m sure that in his native language he could have told us more things quicker and more interestingly.
Thus the importance of a rich vocabulary.
Now, when to use it and when not to use it is a momentous question… (oops did I use that word wrong?) 🙂
Thank you Hugues for a thoughtful reply. I agree about the usefulness of an extensive vocabulary.
But. . . , we have to use that vocabulary to convey information. If we use big words to impress people our thinking tends to become less clear.
A brother in a congregation where we used to live would sometimes say of a Sunday School lesson: “Whoever wrote this lesson must have really deep thoughts, because I can’t understand what he is saying.” Whatever it was the writer was trying to say, he had so thoroughly swaddled it in layers of adjectives and subordinate clauses that one had to guess at what he intended to say. That is not appropriate use of vocabulary.
There is a passage in one of C.S. Lewis’s books where he writes in everyday English, then says: “That is of more than philological interest.” I suspect this five cylinder word sends many people to their dictionaries. Or, if the reader has a smattering of Greek he might deduce that philos means love and logos means word and will conclude that philological means the love of words or the study of words. The point is that in that sentence a five syllable word replaces a lengthy explanation. That is appropriate.
I believe you and I are both philologically inclined. The smattering of Greek that I have comes from reading the etymologies in the dictionary. I feel that the history of a word is as important as its current meaning.
However, if we want to be understood by as many people as possible, we need to lay off the ornamental words and fancy sentence structures. A writer does need an extensive vocabulary to be able to find the precise word to convey what he wants to say. People with limited vocabularies often misuse the words that they do know.
As for your dad’s talks at IT conferences, I doubt that he has any intention to intimidate. He just has the vocabulary to say precisely what he wants to say. That is appropriate in such a setting. I think he has the knowledge of what words mean that he would be able to explain the essence of what he is saying to business managers in terms they would understand.
OK, then I agree with you. That clarifies everything, thanks!