Well, plenty of examples are available online (just google "statement of purpose" examples)
alumnus.caltech.edu/~natalia/studyinus/guide/statement/sampl es.htm
BUT, I think you should do some writing to express your ideas, first. What do you want to do? This is what you are all about, so be excited about writing it.
If I was going to school to be a counselor, for example, I would write all about my insights, personal philosophy, and specific areas of psychology that I love. Maybe I would write about the structural theory of Ronald Fairbairn. You should think of what you are passionate about, and really write something that comes from the heart.
Lets see you write a blog about it, and post it here. Do not worry about if it is "good." Just post your thoughts. What are you excited about?
Kevin, EssayForum.com