Focus on one issue. Don't use big words if more common words will do the job. Use a mix of short and long sentences. Don't repeat yourself. Don't say everything two or three times because you didn't say it quite right the first time.
Repetition turns off readers.
So don't repeat yourself. Avoid telling readers the obvious. Don't waste their time by arguing that education is a good thing or that nuclear destruction is a bad thing. Tell them how to achieve better education or a more secure peace. Look for cliches in your writing.