The main ideas are to make the shower stall fully enclosed, to make it cozy and warm without using as much hot water, and to make it easy to turn the water on and off as needed, with a consistent, comfortable water temperature.
There are actually four specific changes I made in my shower towards this end. For the ultimate shower, I recommend all four, but you can use as many or as few as you want. The total cost is around $100 (depending on many options), but if you want to do it on the cheap, you can also do much of it for under $10.
This project works regardless of whether your goal is to be super-green and have the ultimate low-energy shower (while still being comfortable), or you want to have a super-luxurious shower, while saving a little energy.
Step 1: Four Components
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.