There is one area where you should spare no effort—even if it's not the first space that comes to mind when you think of a party. "The bathroom is the one place your guests are going to be alone," Johnson says. "Concentrate on the sink and the toilet: Make sure there's extra toilet paper out. You want everybody to be able to see it and have access to it." You should have clean hand towels (Johnson recommends the disposable ones from Kleenex) and plenty of soap. You can stash personal effects like makeup or medications in your bedroom or in a box under the sink.