Remove Water Stains: Concentrated vinegar (acetic acid) is fast to remove water stains from faucets and other places. Keep room ventilated. If you dislike the smell of vinegar, use Lemon Juice (Citric Acid), it works a little slower. Keep concentrated citric acid away from dark tile grooves, it may leave a whitish residue.

Keep windows, mirrors and faucets clean: Use Car Wax. The dirt simply won’t hold on. Baby fingers smudging on glass surfaces (TV!) are so easy to remove. Don’t apply on surfaces that hold objects - they will slip off easily. Keep room ventilated while applying.
Waxed windows: The other day I cleaned the garden-side windows, which I had waxed almost a year ago. Just sprayed them over with a hose and squeegee'd. Took all of 2 minutes for a quick shine, and no stripes.
Waxed tiles:  When our neighbor built his new house, the tiling specialist had told him to buff the whole bathroom with carnauba wax for cars and repeat it every year. That stuff is designed to last for months outdoors, so this makes perfect sense to me. Comparing my faucets with those in luxury hotels, I believe a fair number use wax, too.
I did ask, but the room maids wouldn't tell me their secret.

Stop poison from going under your skin: Shampoo, even a few heavily advertised brands (and some cosmetics) contain the same surfactants (tensides) as industrial cleaners. Two of these are known to penetrate the skin and are suspected to promote cancer: sodium lauryl sulfate, including its derivatives and propylene glycol. I searched the Web for the Material Safety Data Sheets which any manufacturer of chemicals provides. Whoa! That stuff  IS dangerous.  I checked all the labels in the bathroom, threw that stuff out and bought safer products. A small expense for peace of mind. And gosh-darn, the hair feels now more healthy and less “flaky”!

Real dirty Hands?  Like blackening grime from working on an engine? That last bottle of not-so-cheap brand name shampoo is now under the sink and does the job it does best. The grime comes off the hands so fast. Seems the industrial cleaner suspicion is well-founded.
Dab a rice-grain bit on wet hands, scrub, rinse well. The skin will feel “etched”. Wash off shampoo residue with soap. Skin may feel rough still, so use a good cream.
Unbelievable, I put such harsh industrial strength cleaner on my scalp for years.

Boycott sham poo! Demand real poo!

Need a safe disinfectant?  Hydrogen Peroxide H₂O₂ sold as Oxydol in Japan disinfects bottles, kitchen tools etc. and leaves a freshness better than any industrial concoction. The distilled water in bottles I bought in Hong Kong supermarkets had an enjoyable taste. Now I know what it was. A few drops of H₂O₂, about 1:1000 of a 3.5% solution prepared from food grade Hydrogen Peroxide. Don’t use any other, it may contain additives and impurities.
The other day I had a sore throat (due to the polluted air in Yokohama) and "cleaned" it with peroxide solution. Be warned, the gargle tastes awful. Next morning, the throat was OKAY.

Air conditioner cooling units develop a musty smell. Chemical cleaners leave chemical residues blowing into the room and may damage the aluminum cooling fins. Hydrogen peroxide effectively solves the issue. Just clean the filter, run the cooler a moment without the filter and spray the H2O2 onto all accessible fins. Reinstall filters. The peroxide does not damage aluminum and effectively removes the mold. It runs into the drain together with the condensation water.
In the environment, H2O2 occurs naturally, near waterfalls, in snow, in rainwater, especially after a thunderstorm has released ozone. Ozone and hydrogen peroxide in tiny amounts are nature's own cleanser.

Ever threw away perfectly usable shirts, pullovers, jackets, pants, because they were tomato stained “permanently”?  By accident (how else?), my wife spilled spaghetti sauce on her new pink turtleneck (of course new clothes are still magnetic to that). Aw! She rushed to the bathroom and then I earwitnessed another accident. She exclaimed, “Look, it goes away! Tomato goes away.”  That was for me to rush. I found her wiping the stains in front of the bathroom mirror. She must have grabbed our sprayer with 3% Hydrogen Peroxide H₂O₂ that stood there by pure coincidence. Hmm, strange. Never heard of this. Try the large stain there - pssht... faints and goes away. WOW! 

Alternative washing powder: After some testing, we prefer the non-polluting American Laundry Solution over the harsh and expensive Japanese variety designed for cold water. Unexpected benefit: we also save the water for the final rinse. There is no soap residue on our clothes which reduces the risk for allergy and skin rash for our children. Heavy stains need pre-treatment with tiny amounts of laundry detergent or the harsh shampoo (see above). 
A friend in Tokyo told me of an inventor who has a water-only washing machine that cleans with ultrasound. Rumor has it that chemical companies pay him for NOT marketing it. If you have any clues, please let me know.

The most beautiful teeth I saw belong to a senior secretary in the Hong Kong office of the company I work for. On a boat tour I asked her and she confided her secret. Her father is a dentist, she said, and found that 80% of the cleaning effect is from the brush. The 20% effect of toothpaste can easily be achieved by brushing longer. Just use plain water, her father had recommended. And that's what she had done all these years. Beautiful and admirable teeth.
I remember a briefing by my dentist in Germany, years ago. He said the “soaps” (surfactants, tensides) in toothpaste actually enable bacteria to slip in between the gum line and the tooth. In these pockets, bacteria are much harder to remove and may cause bleeding and gingivitis. The abrasives (powder sand!) in toothpaste remove the plaque, but also scratch the enamel. And I think the preventive effect of fluoride is barely above the statistical margin of uncertainty. 

An Austrian lady and her husband told me their dentist recommended Hydrogen Peroxide solution for oral hygiene. Haven’t we heard that before? It works for me now.