Choose ideas and information which are not reflected in other parts of your application. This is your chance to supplement your application with information you want them to know. Then work on one paragraph at a time, always trying to include a topic sentence and examples which prove your point as convincingly as possible. Make transitions between your paragraphs. Avoid using the passive voice.
Action verbs capture much more attention.
Use concrete examples. Examples of behavior will often demonstrate an idea more effectively than an adjective. In other words, show how or why, don't just tell. Use exact, concrete language. Avoid vague references, wordy usage or cliche's.