Stuck on statement of purpose: Care to share ideas?

[BenThereDoneThat]

I'm currently applying to schools for I/O, but am stuck on what to include in my statement of purpose as I don't exactly know what admissions committees are looking for. I bought "Graduate Admissions Essays" (http://www.amazon.com/Graduate-Admissions-Essays-School-Choice/dp/1580088724/ref=sr_1_1?ie=UTF8&qid=1323123587&sr=8-1) which has been a great resource and has lots of example essays, but nothing pertaining to I/O and not much in the way of Psych in general.

Does anyone care to share their Statement of Purpose so I can get an idea of what to include/how to frame it?

Thanks in advance.