When it comes to cleanliness, one main rule applies: Stick to the schedule.
With the exception of extreme neat freaks, everyone has times when things get a little messy. But one person's acceptably messy room may be another person's disgusting pigsty.
You and your roommate should agree on what's fine and what's not when it comes to keeping the room habitable. Clutter may be OK, at least temporarily. But rotting food, dirty dishes and foul odors probably aren't. Compromise is important. Be willing to put up with an unmade bed or stacks of books – as long as the bed doesn't start to smell, and the books don't keep you from getting around in your part of the room.
Realistically, though, nobody sets out to live in a room that's a health hazard. Things just get out of control, especially when you're busy. So it's a good idea to set up a cleaning schedule. Agree as to who will clean what and how often. Establishing a day for cleaning might help. Take turns, or divide up the chores, but set a schedule and try to stick to it.
If you're the neater one in the room, don't make the mistake of just tidying up after your slovenly roommate. That will leave you open to criticisms that you've messed with his stuff and maybe even tossed something important. And it will make you resentful. If you find it hard to stick to the schedule, or your roommate isn't cooperating, have a frank discussion. Renegotiate and come up with a plan that's more realistic.
But cleaning is not your primary job. Keep reading for hints about studying.