Sneaky, the trick is to lift your headphones off of your head, if you can hear them with your hands over them, they're too loud. If your roommate's trying to sleep and isn't a deep sleeper, then don't listen to music that'll make you turn into a disturbance. Like for me, instead of listening to Led Zeppelin I'll switch to Pink Floyd. And half the part of coexisting with someone is working out your schedules. If you're in a dorm getting an agreement on sleeping schedules/lights out is a great idea if either of you have early classes.
punqsux, as in, he'd put his dirty laundry in his clothes hamper, clean them, then never put them back into his dressers. So, he'd take unfolded clothes out of his hamper, wear them for the day, get them all nasty and sweaty, and then throw them in the hamper with the clean clothes. Next day he'd just grab another random shirt.
Oh yeah, this kid was also Indian, so you can imagine the wonderful odor that he had going.