Waitlisted..... what now?

<p>so I've been waitlisted to both TSB and HSS. I saw last year's thread, and I'm trying to write a letter saying that I want to keep my name on the waiting list and some of the achievements that I've made since I've applied... but who do I send this to?? is this what I'm suppose to do?? and I heard theres a priority waitlist for cmu.. how do you put yourself in the priority waiting list?? help :S</p>