Leaving the water running can waste a lot of water. The shower uses 2 gallon of water per minute, you shouldn’t wait to get in, it will heat up. When you brush your teeth the sink doesn’t need to be on the whole time, just you it when you need to rinse the brush not when you’re brushing. Washing the dishes doesn’t need the water on unless you are rinsing but when you are washing turn it off. It’s the little things that can save a lot in the long run.