Well here are some general tips for LOCI's.
Keep them short, no more than a page. Two paragraphs seems appropriate.
-Include a short introduction like "thank you for taking time to consider me and give me an opportunity to attend your school."
-Tell them any relevant news about you, like what you have been up to, any changes in GPA, any significant accomplishments since you first applied.
-Express how much you want to go there and why the school is a good fit for you. A lot of times they waitlist applicants to see which ones are actually serious about going there, which ones know something about their school, and which ones just applied for the sake of applying.
-End with a short conclusion like "Please let me know if you require any additional information from me that will help in your decision."