Avoid flushing the toilet unnecessarily. In other words, don't use it for garbage. Dispose of tissues, insects and other similar waste in the trash rather than the toilet.
Test for a leaking toilet by adding food coloring to the tank (not the bowl). Without flushing, note if any color appears in the bowl after 30 minutes.
Install a low-flow toilet. If you have a standard toilet, put a toilet dam in the tank. Do not use a brick which will disintegrate and clog your pipes.
Use a low-flow shower head.
Install aerators on faucets.
Don't let the water run when washing, brushing and shaving. Turn it on and off as needed.
Take showers instead of baths. A ten minute shower with a low-flow shower head uses half the water of a regular bath.
If your shower takes a while to heat up, and you have to let the water run, put buckets in the shower to capture the water for watering plants, washing vegetables, water for pets or washing your car and bike.
If you are designing your own bathroom, think about putting in the Japanese style of tub that is deeper but more compact - water cools more slowly requiring less input of heated water.
Get a small sand timer that lasts about three minutes and bring it in the shower. Most people can have a shower in six minutes.
Turn down your water heater when you are going on a long trip.
Get free distilled water for irons and humidifiers by straining rainwater through 2 to 3 layers of panty hose.