Choose your topic wisely. This applies whether you're writing your college admission essay or any thereafter. Focus on one topic that you can elaborate on in detail. Don't pick a topic you think others want to hear about (unless, of course, you're assigned a topic). Write about what's important to you and show why you can speak with authority about the subject.
Write in your own voice. Don't try to impress professors or admissions deans with "SAT language" transposed from the thesaurus. As author Stephen King famously said, any word you have to hunt for in a thesaurus is the wrong word. Tell the story of your essay as you would tell it to a friend, but with only sparse use of slang. Avoid profanity.
Appeal to the senses. The adage and cliche "show, don't tell" remains in the professional writer's psyche because it's sage advice. Don't impress others with abstract ideas; move your readers with precise detail and imagery that invites all the senses. Provide facts, but complement the facts with the story that shows why they have relevance.
Remove unnecessary words. After you've written your first draft, remove words that don't add meaning to your essay. In the case of an admissions essay, the traditional length is 500 words. Take note, also, of your grammar. Consult the book, "The Elements of Style," to refresh your understanding of clear, correct and active language.
Take some risk, but not too much. Parke Muth, in talking about writing style, says that to err on the side of the baroque might not be as bad as to stay in the comfort of the boring. Captivate your readers with a compelling introduction, but remember to appeal to, and respect, a diverse audience without diluting the story or sacrificing sincerity. 'Tell it like it is' with words 'seasoned with salt.'