The following is a checklist for this type of panic:
Sound
Turn off the television and tune the radio (low volume) to a soft rock, middle of the road or classic rock station.
Sight
Turn on every light in the house (day or night) and open every drape and blind (day time only).
Odors
Heat some frozen pastry slowly in the oven or heat a pan on the stove and then drop in a few drops of vanilla.
Kitchen
Wipe kitchen counters, place dirty dishes in dishwasher.
Bathrooms
Wipe counters, flush and close toilets.
Living/Family Rooms
Hide magazines, newspapers, and games; remove clutter.
Bedrooms
Straighten beds. Hide clutter under bed (not in closet).
Exterior
Put away toys and clutter. Keep walk clear.
Children & Pets
They are a distraction, so send them outside.
Goodbye
Sorry, but this is the single most important thing you can do in a showing to help sell your home! Even if the showing agent insists that it is okay to stay, you must leave. Buyers must get emotionally committed to your home to buy it and they cannot become emotional about "their new home" if you, the current owners, are "hanging around." Please, at the very least, go into the backyard. Even better, go to the store.