Be sure to rinse the container and change the water every few days. When washing or shaving, partially fill the sink basin and use that water rather than running the tap continuously. Use short bursts of water to clean razors. Likewise, when brushing your teeth, turn off the water while you are actually brushing, instead of running it continuously. Use water from a mug for rinsing.
Short showers use less water than baths.
If you still prefer bathing, avoid overfilling the tub - one half full should be enough. Check regularly for toilet tank leaks into the toilet bowl by putting a small amount of food colouring into the tank and observing if it spreads to the bowl without flushing. Repair leaks promptly. Likewise, regularly check for leaks at the base of your toilet, and have any promptly repaired. Never flush garbage of any kind down your toilet.