I've published a college application planning timeline to take you through the college admission process from start to finish. This is the fourth article in the series. (Read the first article.)
3-4 months before submitting your college applications:
Focus on your college essay. Write an initial draft of 1300-1500 words, wait a few days, then aggressively reduce its length so that it will be concise, yet full of substantive content. Print draft after draft. It's often easier to make revisions on paper than on the computer screen. Show your college essay to trusted friends, family, and your guidance counselor to get feedback on your rough drafts, and, ultimately, your final draft.
Look at your résumé further and make sure that it's current. Edit it for both style and wording.
2 months before submitting your college applications:
Take another look at the applications for the colleges to which you're planning to apply and make sure there haven't been any significant changes from last year's versions.
Determine whether you might be able to write a diversity statement. Of course, most people who write them consider themselves under-represented minorities (race, ethnicity, sexual orientation, etc.). However, even if you don't fall within one of these categories, you might be able to write one if you've had an unusual life experience or can bring diversity to the table in another way.
Check whether each school asks a question along the lines of "Why do you want to go to our school in particular?" (aka "Why X?") If they ask this question, be sure to answer it. To gather the specifics necessary to answer this question, visit the school's website. Visit the school in-person, if possible. Talk to current students and alumni, and be as specific as possible in your reasons for wanting to attend the school.
Schools will typically allow you to write an optional essay or addendum on any topic (including weaknesses). If there's a topic you weren't able to cover in the other essays, consider doing so here. (If a school doesn't ask a "Why X?" question, you can provide your answer to such a question here.)
All of these essays should be reviewed by trusted family/friends, as well as your guidance counselor.
Check your application account(s) to see whether your recommenders have submitted their recommendation letters for you yet. If they haven't, follow up with them.
Request your high school transcripts. Your school will have to submit transcripts directly to colleges.