What are the various tools and processes writers should use to ensure that their work clearly conveys their intended message ?

Hi! There are many tools and effective way for a writer to convey his/her intended message to the audience, here is a list of what I know and use for argumentative essays:

1. Emphasis through word connotations-some words can play powerfully to readers to focus in on a sentence or phrase. If you need to make a point to the readers, use positive, aggressive, powerful, negative word connotations to sway the audience. "the investigator observed the dark dripping blood from the old rag that now streamed along the mutilated body of the victim."

2. Syntax and Sentence Structure- you may have notice short choppy sentence in books and narratives. Writers do this for the purpose of emphasizing on a point. "and then there was none." The points they zoom in for the audience are usually important and can convey the intended message when used properly. 

3. Rhetorical Questions- "But wouldn't you have done the same thing?" Rhetorical Q 's are used to emphasis, persuade, and influence the audience to do or think a certain way about a subject. This is a very powerful tool to convey a intended message to the audience. 

4. Polysyndeton and Asyndeton- You may or may not have heard of this but (Polysyndeton) is the Repetition of conjunctions in a series of words (but, and, etc.) while (Asyndeton) is the Omission of conjunctions that normally join words or phrases (NO but, and , etc). This skill and tool can effectively place emphasis on a message. Asyndeton-"He carried the burden of a father, a worker, a friend, a partner" Polysyndeton- "to give a better opportunity to the workers and the bakers, the chef and the maid, the servant and the slave.
5. Other tools you can look for: closing conclusion containing message, other rhetorical devices, opening thesis...etc :P