Before starting to clean a room, it is important to make sure you have permission to clean it. Even the kindliest homeowners will complain if they find you, a stranger, in their living room running the vacuum cleaner, even if you wait until after everyone has gone to bed. They may be angry. They may not even have carpets.
Once you may clean a room, you should determine whether the room needs cleaning. Cleaning a room that is already clean gets you no credit for your work. If it isn't obvious whether the room needs cleaning, have a friend need a new toaster oven. Then, out of friendship, you could offer to e-mail a picture of your own toaster oven. When getting your camera out, you're certain to notice that the background too untidy to photograph, and so you know to clean the room. If you are trying to decide whether to clean a room other than the kitchen, move your toaster oven into the appropriate room, which you can do while waiting for a friend to need a new toaster oven.
Much traditional housecleaning lore recommends starting from the top of the room and working your way down, and it is wrong. In normal climates the top of the room will be populated by spiders. But spiders are good things to have: they will spin their webs adding considerable atmosphere and flammability to the most basic room. Furthermore they will eat small and unpleasant insects, as well as monitor your children's Internet usage. If you protest that you do not have children, look again, closer to the ground this time. This could explain those mysterious running noises, slamming doors, and appliances left on, not to mention the missing snacks from the fridge. In any case you can't suppose the problem is with the spiders, so let them alone.
In a warmer climate the spiders will be replaced by geckos, who are more eager to work in the awful heat. But again you should not sweep them off the ceiling. Losing one's footing on a simple flat surface -- even when being swatted by a broom over a hundred times their size -- is a grievous embarrassment in gecko society, and those geckos you have victimized this way will seek revenge. You're likely to find one night after you've crawled groggily into bed that an army of dozens of tiny geckos have gathered by your side, ready to launch an attack dependent on their very sticky hands. Then you roll over, crushing them all in one horrible moment, and when you wake up five hours later you feel guilty, not to mention disgusting and gooey. Far better not to start trouble.
When it's warmer still the ceiling will be a semi-molten surface holding back pools of liquefied lead. This is a sign that your room is on Venus. While it's important to be clean, you don't want to risk damaging your walls, since this may let in clouds of sulphuric acid vapor which, while it will peel the dirt off your walls, will also peel the walls off your walls. Consult with your local geckos to be sure.
Starting from the bottom and working your way up may sound like the obvious alternative, but this has the problem of putting you on your knees to work all around the room, and then get dizzy when you stand up. As part of the cleaning process, then, you should cover the floor with soft objects -- pillows or sofa cushions will do -- so that when you stand, if you fall back down, you won't get hurt. This means you will have to mess up the room as quickly as you clean it, although it will be a more organized mess.
This obviously leaves starting in the middle, but for the typical room the middle is filled with air, which is very difficult to clean. You can try to spray glass cleaner on the air and sweep a paper towel around, but it won't be noticeably cleaner when you're done. Therefore, the best approach is to not clean the room, so advise your friend to keep the old toaster oven.
Trivia: Samuel Curtis Johnson began selling wax for parquet flooring as sold by his Racine Hardware Company in 1882. Source: Dust, Joseph A Amato.
Currently Reading: Eniac, Scott McCartney.