When the realtor is coming to show your house and you have had the flu and your kids have rampaged and ruled the roost for three days, eating and leaving crumbs on every surface, taking each cushion off the couch to play "lava", and washing the muddy dog in the tub...
Shove everything into closets, under beds, and in baskets that also stack into closets.
Delegate someone to vacuum duty and sweep crumbs under the rug.
Close the shower curtain and toilet lid and pray no one looks in there.
Straighten rugs and dining room chairs and make beds as you run from top to bottom or from back of house to front, so you can grab the kids and escape out the door seconds before the realtor's car pulls up in the driveway.
My five year old says this:
Him: Just speed around and clean it up! Put it back where it's supposed to be.
Me: You don't wear roller skates or something to go faster?
Him: No. Just go zoooom!
If the In-laws are coming over and you haven't had time to clean, pick a room and throw all clutter in there, shutting the door. Do everything you can to distract them from nearing that door. Share pictures, take pictures, feed them, offer to take them out, watch a DVD, spend hours talking shop in the garage, go outside, play cards, or a board game; do anything!
Maybe you could let the dog lick the dishes clean. Either in front of the in-laws or not, your choice.
Some animals make good dusters too.
Umm, I'm out of ideas. So I'll leave it at this.