Quick question: Are you writing this for your application next year? Because I think it may be a little too late to seek out a congressional nomination for class of 2011.
When writing you could do the whole "Why I deserve to attend AFA" schpeel (what i did lol) it works, but dont be afraid to put a little heart into your letter. I could explain what "heart" is but seeing as how you want to attend a service academy I assume you already have a good idea.
Uhhm... sound intelligent, confident and strong, even if what you say goes against your congressman's political views, it shows your untimid and have a strong resolve. Write about what exactly you want to do as a commissioned officer in the Air Force and more importantly, how you will go about doing it and getting there. Try not to be too cockey, I know its hard but there is a fine line between highlighting yourself and undermining other candidates.
I dont know if it was wise on my part mentioning my plan B of Norwich University and Army ROTC as it may have diminished whatever confidence Idisplayed, but also gives a "steadfast, never quit" feel.
AND MOST IMPORTANTLY!!!!!!
be prompt
, dont be like me and wait until your rep doesnt have any nominations left to give out