Just bring a sleeping bag, pillow, flip flops (for the dorm), extra clothes, and pt clothing (basically anything you don't want to get dirty.
Also, if you do PT, bring sweatpants, and wear them OVER a pair of shorts. I did an overnight and was offered to go to Ranger PT the next morning (I thought I was observing, not participating, needless to say, I was not prepared at all for it) and we were told to take off sweatpants and sweatshirts. Good thing I was wearing shorts underneath. Haha
Also, bring some $$