have you already met this guy before for one of the one-hours??.....I really hope so!!.........
treat the overnight like you're hanging out with a buddy......don't overplan it (don't cram too much into the schedule), ask what he'd like to do, give him some time to himself to do some personal chores (as suggested upthread)......
are you ok sleeping with somebody in the same bed?....or same room?.....(I'm not)
smile, don't try to impress him, talk slowly, be yourself