I tried combing through the threads here but didn't find anything solid on the topic. I know some programs don't put too much weight on these, but I want to make sure just in case. Any tips would be appreciated.
Straight to the point. No bull$*** or fluff. Just tell them why you want to extern at their program (usually includes "I heard through my classmates/faculty/internet message board that this was a solid program worth checking out"). Don't make this a personal statement. You can hurt yourself more than helping yourself with this one. Good luck.
I'd stick with what they said. Make it short and sweet. Also, it's fairly likely that no one is going to read it anyway, so you can take that to heart.