Simple words and constructions and short sentences are often best, but variety does prevent boredom. It is important to integrate quotations into the fabric of your argument. Use appropriate conjunctions and punctuation.
Formal writing is always polite.
It is not acceptable to use masculine nouns and pronouns to refer to men and women. For example, man is a literate being. To avoid sexist language, the plural is often the best solution grammatically. For example, people are literate beings. Avoid writing the way you speak.