Write each person's name on a clothespin and line them up to the far end of the washing machine. When it's their turn to do laundry, they will move their clothespin to wherever their clothes are. Place it in between the washer and dryer if they are in the middle of more than one load.
If you don't have something to clip the clothespin to, then stick a command hook on each appliance to clip the clothespin to it.
I like having one for our guests, too. :)