Write an article based on this "Write a few drafts. Proofread for typos. Have a friend look over your letter. Send your letter out."
You want to make sure you write a few drafts of your proposal. After writing the initial draft, set it aside for a few days. Then, look it over after you've had time to think. Rewrite the letter, adding in any new information or insights you thought of. If you have time, try to write at least a few drafts of your justification. You should not turn in a job justification with typos. Proofread the letter a few times, making sure it's free of spelling and grammatical errors. It can be difficult to catch your own typos, but there are some tips and tricks that can help.  Give yourself some time. You're more likely to catch typos if you set your work aside for a few days. If you don't have a few days, try setting it aside for an hour and then rereading. Print out your letter. Changing the format from which you're reading can help you better check typos. If you don't have a printer, consider changing the font type or color. You can also try reading your letter from the last paragraph to the first. Force yourself to reach each word by placing the tip of a pencil against the screen or page. Reading your letter out loud can also help you focus on each word. A second set of eyes can catch typos you may miss. People often go "typo blind" when reading their work, meaning they miss their own errors as they read what was written in their head. Having a friend read your letter over can help you catch typos. Once your letter is professional and polished, send it out. Make sure you send it out the proper way. If your company uses wooden cubicles for physical mail, print it out and put it in the cubicle. If your company prefers e-mail attachments, e-mail the letter to your boss.