Your essay is perhaps the most important aspect of your college application. A really good (or really bad) essay can mean the difference between being accepted or denied admission. A student who has an otherwise outstanding application may very well be wait-listed or even denied if their essay is weak or poorly written. Along the same lines, a stellar essay may just convince an admissions committee to accept a student with a less-than-perfect academic record.
The point is, by the time you start filling out applications, there isn't much more you can do to change the facts about your high school career: grades, test scores, activities, achievements -- are all final and in the past. But your college essay is the one thing that is entirely in your hands. Writing the essay is your chance to speak directly to admissions staff and show them that you are too good to be turned down.
Check out the other links in this section to learn more about writing a great college essay.