Then hie thee hither over to Sisyphus's place, where not only will you pee yourself laughing, but the comments on the kinds of things to focus on in an STP are really helpful. In my grad program, we were asked to write an STP in our TA training course. Our TA training course! Like, our first semester of teaching as TAs! I tried, was told I was doing it totally wrong, and then refused to do the assignment on the grounds that it didn't make sense for me to write such a thing after four weeks in the classroom (especially as I had just come out of working for a few years after Grad School Parts One and Two).
Anyhow, I somehow made it to graduation despite my defiant attitude -- and now need to write an STP. Of course now I have more to reflect on, and I realize I write so much STP-like things in my letter that maybe having the STP there will give me more space in the letter. (At least I might actually have margins -- just kidding.) Here's what I'm doing: I'm taking all the good comments that people suggested at Sisyphus's, turning them into questions, and free-writing. Perhaps that's what I should say in my STP too -- that I believe in tricking one's self into writing at every point. Tee hee.