Pick a single square foot right in front of the door and clean that. It won't take long.
Do that over and over until you've gotten to something else: dresser, desk, whatever. Pick a single square foot on that and get going. Everything that isn't where it belongs, take it to where it does. Don't worry about the condition of where those things go at the moment, you'll get there. Get the surface organized. Repeat as necessary until the surface is cleared.
Repeat as necessary until you've gotten to every piece of furniture in the room.
Have a trash can on hand for this. You're going to discover a tornado of trash paper. Just get rid of it.
Clothes hanging around that don't fit, bad style, damaged? If it's fit or style, bag it for a donation. Damaged, just toss it. Thrift stores don't do damaged clothes - not the good ones.
Repeat as necessary.