I've changed four things in my shower to make it cozier, and to make it use less energy and water. They can be used alone or in combination--you might start with one or two and start saving right away, and consider doing more later.
The four components are:
A) Enclose the shower stall fully, to keep it cozy and warm inside, even when the water is off. The idea is the same as the Shower Dome
, available in New Zealand for about US$300, installed, but costs much less!
B) Pedal-controlled water flow, so it's easy to turn the water on and off, and modulate the flow as needed.
C) With the water fully shut off at the showerhead, either with the pedal control or with a conventional button valve at the showerhead, mismatches in pressure can make the hot water back-feed the cold water or vice-versa. When you turn the water on after it's been off, you get a blast of hot or cold water. If you have this problem, there's a plumbing trick that can solve it.
D) Choose your showerhead carefully. Some low-flow showerheads chill the water by evaporative cooling when they atomize the water into a fine spray. Then you need to use more hot water to stay warm. There are better showerhead choices.