Format for Supplemental "letter"

<p>You know that last item on the supplement. a letter from a parent/teacher/friend?</p>

<p>My friend wrote me one but is sketchy on the format. Should it be formally addressed, using formal diction? Or just a casual letter talking about, casually, the particular merits of <em>me</em></p>

<p>see dat sexy body go bump bump bump</p>