Clean the toilet. This is enemy number one, especially if you have a boy of the errant pee variety. Give the bowl a quick scrub and wipe down the seat.
Wipe down surfaces. Remove any personal items to keep surfaces clear. Use the current hand towel to wipe the sink, mirror, and any other dusty surfaces. Hang a fresh hand towel, which will immediately make the room look cleaner. Empty the trash can and wipe that down, too, if necessary.
Stock up, and light a candle. Make sure there's extra toilet paper and plenty of hand soap. Then light a candle to make things smell fresh.