Plenty Of TP
Check the supply of your guest bathroom before you have people over. If the roll of toilet paper is low, go ahead and switch it out for a full one. Don't forget to place an extra roll somewhere visible. This will prevent your guests from having to search through the cabinets if they run out.
Clean It Up
Give your guest bathroom a good cleaning before you have visitors over, even if it isn't used very often. Pay special attention to the toilet, countertops, sink and mirror, but don't forget to empty the trash cans and put out clean hand towels!
Brighten Up The Room
Consider adding some flowers to give the room some color. Other things, like a basket of magazines or a bowl of potpourri, will add character to the room. Stay away from heavily scented candles, because some people may not find them appealing. However, do provide air freshener in case the guest needs it.
Point Them In The Right Direction
If you do not have a designated guest bathroom, decide which one you will be directing your guests to use. People may feel uncomfortable using what they feel is your private bathroom, so make sure all personal toiletries are out of sight.
If your guests will be staying overnight, make sure there are extra toothbrushes and toothpaste they can use if they forgot their own. Even with the most meticulous packing, things can be forgotten, so save your guests an unnecessary trip to the store. Placing clean, folded towels out in the open will keep your guests from having to ask.