I have to agree with Mrs. Clean in that the first step is to pick up and declutter. And I also have to agree with jgalves in that he may have an issue with letting go of his clothes. If the issue is that he does not put clothes in their proper places (dirty clothes basket, drawers, closets) then he has to get organized by adding these steps into a normal routine. If he does not go through the motions of putting clothes away, then it is a continous cycle.
If it is because he can not let go, then the issue is deeper than feeling a bit lazy and will take loving intervention to assist him in getting better.
On a side personal note, I find it wrong that he does not put the care and consideration into his room but require that you "some how" clean it for him and this would prove tiring in the long haul because it would continue to happen. I personally would not eat/drink something and leave the dishes on the table because the other person is "responsible" for the cleaning. I do the laundry in my household because I have a lot of different little things I do with it, so instead of "requiring" my boyfriend to do it, I do it. But because I do it, I don't believe my boyfriend should be able to throw clothes on the floor, leave things in his pockets, or to demand "how" I should fold his pants.
If you do not mind picking up after him then the first step would be to pick up, declutter and start the laundry with dirty clothes. But no matter the reason, the first step would be to determine the reasoning behind the clutter issue, that way you can figure out what step you wish to take next. Communication is vital.