Begin in the Bathroom

Start out in the room that has the greatest gross-out potential, and then narrow your focus onto the area that could be the greatest offender: the toilet. Since you're in a hurry, squirt a cleanser under the bowl's rim, let it sit for 30 seconds, then quickly swish with a brush and flush. Your goal in this case is to remove stains, not disinfect. (Leave that for your actual cleaning day.)
Think About the Sink

A sparkling faucet gives the illusion of a clean space. Grab an always-useful disposable cleansing cloth to remove drips and splats and add shine to the sink's faucet. Then use it to wipe down the basin and the surrounding countertop. Afterward, eyeball the corners of the floor for piles of hair and dust, using the same cloth to pick them up and toss them.
Straighten Up

Nothing peps up the washroom quicker than a few thoughtful touches. Straighten your bath towels and replace the hand towels with fresh ones. Toss personal products into drawers or under the sink. Close the shower curtain or the shower doors. Fluff and straighten the bath mat. Make sure there's enough toilet paper. And finally, empty the garbage bin on your way out.
Conquer the Kitchen

After taking care of the bathroom, move on to another guest favorite: the kitchen. Survey the area for clutter that needs to move, and then get creative about where to stash it. Dirty dishes, empty pizza boxes and the like can easily find a temporary home in places like the pantry, a cabinet, the credenza, the dishwasher and even the oven. Just remember to move them back to their proper place once your guests have left!
Clean the Countertops

The cleaning wipes you used for the bathroom are just as helpful in the kitchen—as is a dishrag and a few spritzes of an all-purpose cleaner. Wipe off the sink faucets, do a quick swipe in the sink, then hit the countertops. Clean off the oven top (if there's time), and finish up by emptying the trash.
Streamline Your Stuff

Will visitors lounge in the living room? First, fluff the couch pillows and refold any throw blankets, after which you should concentrate on the surface that collects the most clutter: the coffee table. Don't sweat hiding the magazines, toys and remote controls that congregate there; simply organize them in orderly stacks. In your short timeframe, the items to consider removing are empty drinking glasses (stow them in the kitchen, preferably in the dishwasher) and private papers like bills or contracts. (Prying eyes are less likely to spy them if you place them in a bedroom and close the door.)
Tackle the TV

Your television is one of the largest pieces in your living room—and is often one of the most noticeably dusty. Use a dry cloth to quickly (but thoroughly) wipe down its screen and base. And when guests arrive, make sure it's turned off. Opt instead for low-volume music playing from a computer or mobile device, using an ads-free, no-brainer Internet radio app.
MORE: 10 Must-Clean Home Zones
Light the Way

Make guests feel welcome in a room that naturally glows. On a sunny day, open the blinds or the curtains; if it's nice outside, crack open the windows for fresh air. If your unexpected visitors arrive in the evening, light a scented candle and use table lamps instead of overhead lighting. Not only will a darker, cozier room mask a little messiness, but a lit candle will also help remove any unwanted odors.
Don't Forget to Breathe

Remember: Your friends won't be judging your home nearly as hard as you think they will. Relax a little and enjoy the gift of time together. And if all else fails, simply pour your guests (and yourself) a glass of wine—everything looks slightly better when the vino is flowing!