This may seem strange, but I started thinking about how I could make small daily changes in my life to use less water. One task that I feel I use entirely too much water while doing it is shaving. One could go electric, but I won't. Instead of letting the water heat up and turning the water on and off, I realized I could heat a kettle of about 3-4 cups of water. Not only do I use less water, but the water stays hot the entire duration of shaving. My three roommates now follow my lead and shave their face in the same manner.
We also have a new toilet flushing rule, but I won't go into detail on that one.
May seem silly, but it is the little things that are easy to adjust. And that is where most will start to implement change.