This is a summary of Baldesar Castiglione's advice in "The Book of the Courtier" on how to write. I can fully understand why the Elizabethans were inspired by reading this book. It is timely advice for our "sloppy" age too:
Writing is a kind of speech which remains after it has been uttered. So a greater effort should be taken to polish one's writing than one's speech. One's words should not be different from words in common speech, but they should be selected from the most beautiful words of all those used in everyday speech. The finest speaking resembles the finest writing.
As for archaic words, they can beautify one's language through their force and eloquence, and embellish what one writes. A perfect courtier must know both how to write and how to speak. The voice should be sonorous, resonant and well articulated, with clear enunciation and suitable manners and gestures. Clarity should go hand in hand with elegance.
All the ideas conveyed should be either beautiful or witty or shrewd or elegant or solemn. One should clarify every ambiguity without being pedantic. A writer and speaker should be able to communicate with dignity and emphasis, and arouse our deepest emotions. In doing this, one shall shall soon find one's language adorned with fine phrases, figures of speech, metaphors - even a good medium for literature.
The Italian language should be "universal, rich and varied like a lovely garden full of all kinds of flowers and fruits". Some linguistic qualities are good in any and all languages, for example, fluency, logic, richness, well-constructed sentences and harmonious clauses.
It is wrong to force any writer to write like someone else for whom he or she has no natural affinity. We should all express own thoughts and in doing so, follow our own deepest nature.