It is important to put yourself in the shoes of the Admissions Officer: why would your personal statement be unique, how are you different from the other candidates? Primarily you need to decide how you will divide your personal statement into digestible chucks. The most obvious way is to divide into paragraphs of 100 words. If you aim for between 500 and 600 words at most, it will help your admission officer when they have to read thousands of personal statements to find the perfect student.
The PS should always end on a positive note, and the conclusion should summarize the body of the statement. It is important to reiterate the primary message of the personal statement and thank the audience for their consideration. This will leave the reader with positive images of the applicant as they put the personal statement down.