Some college applications require you to answer a set of very specific questions. It's advisable to answer the questions asked. In some cases, one of the questions may ask for further (non-specific) information, and that's where you can write freely about yourself and your interests.
The best form of expressing yourself in writing in an academic setting is by way of the essay, so organize your statement according to the essay form. Your reader should clearly recognize an introduction, a body and a conclusion.
Whether you are responding to a general or a specific question, begin your personal statement with brief information about yourself. The reader may or may not already have an idea who you are, but don't take that chance. State your name and your background at the beginning of your first response, or in the introductory paragraph of your essay.
Unless you are given instructions to the contrary, the body of your personal statement essay should be a story about you. The Purdue Online Writing Lab (OWL) provides a great set of questions to help you shape your story. One particularly helpful set of questions suggested there concern the personal or family problems, history, people or events that have shaped you or influenced your goals. Those details will help the committee better understand you or help set you apart from other applicants. (See reference 1).
Your story should be well-crafted with clear, specific details that flow smoothly from point to point, and the lesson(s) learned should be clear to the reader. When you're done, you should edit the story carefully for spelling and grammar mistakes, and also for tired or over-used phrases (clichés).
It is more than likely that your reader will be someone who is not in your peer group, so choose words and references that are universal. And if you do use peer-specific terms, provide the reader with a brief explanation for those terms.
It may be tempting to send the same personal statement to every college you apply, especially if you're applying to several, but the applicant who takes the time to specify why he or she has chosen each college is more likely to impress the admissions audience more than the one who does not.