Step 1 take a week vacation from work. Get your room spotless clean in that week.

Step 2 get a garbage can to keep in the room. Also get a laundry basket that you immediately throw dirt clothes into.

Step 3 always immediately as you make a mess or have garbage throw it in the garbage can. Also as soon as you get done with anything put it back where it belongs. When the garbage can gets full immediately take the garbage bag out and replace with new one. And take the full garbage bag to the dumpster.

Doing this helps keep your room relatively clean at all times with all you needing to do is things like dusting, sweeping and mopping floors if non carpeted or vacuuming if carpeted once a week or two. And is something you can take care of fast if your girlfriend is coming over and it hasn't been done for a bit.