Go through all clothes and get rid of the ones you don't want or need anymore or bag them to donate.
Throw away anything you don't need anymore and throw away all trash and put dirty dishes away.
Put everything away and clean off everything. Spray everything down and sweep and mop.
Cover the floor and anything that you don't want to get paint on and begin painting the molding and then the walls.
While waiting for paint to dry map out and plan how you are going to have the room.
Put in all the new furniture and decorate the room. Put in all the final touches.