I. Conserving indoor water in general

1. Save water from your taps. Turn the faucet/tap off while you are brushing your teeth, shaving, washing your hands, doing dishes, and so on. Turn the tap off when you shower, too. Get wet, then turn off the water while you soap up. Turn it back on for long enough to rinse. Look for a twist valve that installs behind your shower head to keep the water temperature where you set it while the water is off.
Use a bucket or bowl to catch the cold water that comes out of the faucet, tap, or shower while you are waiting for the hot water. Use it to water plants or pour into your toilet reservoir after flushing.
Water from a hot water tank may have more sediment or rust than water from the cold water tank, but is otherwise suitable for drinking. If you use a water filter, you can filter the saved water, and put it in bottles in the refrigerator for drinking water.

2. Check your plumbing for leaks, especially leaking toilets and faucets. Fix anything you find leaking. A silent toilet leak could waste from 30 to 500 gallons every day!

II . Conserving water in the bathroom

1. Install low-flow shower heads and faucets or faucet aerators. Low-flow devices are inexpensive ($10-$20 for a shower head and less than $5 for a faucet aerator). Most simply screw into place (you may need an adjustable wrench), and good, current units maintain the pressure and feel of the flow while using as little as half as much water as conventional units.

2. Take shorter showers. Take a timer, clock, or stopwatch into the bathroom with you and challenge yourself to cut down your showering time. You could even play music while in the shower and challenge yourself to cut down the number of songs it takes you. Shave outside the shower, or turn off the shower while you shave.
Take showers rather than baths. By taking a bath, you are using up to 100 liters of water! Showering will generally use less than a third of this amount. See the water use table below.
Install a valve that fits just behind the shower head. These valves are inexpensive and simply screw into place. Turn the water on for long enough to get wet. Then, use the valve to turn the water off while preserving the temperature of the water while you soap up. Turn the water on again to rinse.