Plan ahead. If you are not already a strong writer of English, you will need to hone your skills. Allow at least a few months.
Visit your high-school English teacher or a college writing professor with a page-long sample of your writing and ask what, specifically, you should study. Many ESL students have trouble with tense, subject-verb agreement, plurals, prepositions and infinitives. You may also misunderstand idiomatic expressions; for example, in "drop by my office", the words "drop by" are not meant to be taken literally, but rather stand for "visit."
Practice by writing and correcting paragraphs. Grammar check will help you when your teacher can't. When you are satisfied that you can write a good paragraph in English, you can move on to writing your application essay.
Make an outline or allow yourself to free-write. Free-writing works well for people who need to write to formulate their thoughts and discover the essay, rather than preconceive it. You can cut irrelevant material and organize it in another draft.
Open with an anecdote, and then tell a story about yourself that circles around a central idea, perhaps your passion for history or cooking, or you might explore how your family celebrates important events. A central idea will help you to focus the essay and give it a unique spin that lets the reader see you as an interesting person. Foothills College, a community college in California that often helps its students apply to four-year schools, recommends this approach.
Transition to specifics about your accomplishments, your goals and why you want to study at the college in question in the last three paragraphs. Don't brag or puff up your accomplishments, but do be proud of them. Also, don't try to flatter the college. Just tell the truth about your reasons for wanting to attend the school and what you know about its reputation.
Print out the essay and proofread it on paper by reading it aloud. You will catch more errors this way. Go back to the computer and fix any errors and proofread it on hard copy again. Do this as many times as it takes to get a good copy.