Show that you're interested and that you've taken the time to learn about the program. Take careful notes on each program and note where your personal interests, qualities, and accomplishments coincide. One size clearly does not fit all. Many applications require that students address specific questions in their admissions essays. Make sure that you're answering the question.
Some applications offer a string of questions.
Pay attention to your responses and try to avoid being redundant. As you begin write, remember that this is your chance to present your strengths and really shine. Take advantage of it. Discuss your accomplishments, valuable experiences, and emphasize the positive. Make it involved and engaging.