Reducing your water usage is easy, and it doesn’t mean you have to brush your teeth with a pinecone or weep with remorse every time you flush the can. As is the case with all resource usage, responsibility starts with understanding how much of something is actually needed to get the job done. Until you take that step, you’re basing your behavior on assumptions and habits you learned as a kid.1
Use dual-flush toilets.2
Install them. Use them. Hit the right button.
Low-flow showerheads and faucets squirt sufficient amounts of water at you. Get in the way of the reduced squirt at the right moment, do your thing, and turn the water off. Easy.3
Purchase a PHID (portable humanoid insulation device).
It’s hard to exit a hot shower on a cold day. Buy a great robe and hop out of the shower a minute earlier.
Buy natural. Buy bulk. Use less.
Consider all the products you use in the bathroom: cleaning products, cosmetics, other stuff. Think of all the packaging. Think of all the chemicals. Think of all the bunnies. Act accordingly.
Consider solar hot water.
Either install a fancy black outdoor water bag for plein-air showering or spend some dough on a roof-mounted solar water heater.