The NCTE recommends four ways to polish your writing in this skill brief. Two of them bear special focus.
The first one, reading your drafts aloud, will help you to pick up awkward phrasing, poor word choice, redundancies, and overlooked errors in grammar or punctuation. I have used this approach when coaching writers ranging in age from 18 to 80, from education levels of high school graduate to post-doctoral fellow, from scores of fields and from hundreds of companies--and it always works.
The third one, imagining your readers, is easier than you might think. Pretend you are in a dialogue with them. So let's say the first sentence of a proposal to your boss says, "I need a laptop."
What would your boss ask? "Why?" Now that first sentence would say, "I need a laptop to be more productive when I am in the field."
Then your boss might ask, "How often are you in the field?" or "How can you be more productive in the field?" Now you would write, "Using a laptop during my 12 hours in the field each week will help me produce my investigative reports more efficiently."
Then your boss would probably ask questions such as "How many investigative reports do you write weekly? How backlogged are you in writing these reports? Can you get help writing these reports in some other way? How much does the laptop cost?" You get the idea: write to your reader.