Save water, energy, and money by getting a low-cost shut-off valve for your shower.
You can install a shut-off valve like this one just behind your shower head. It shuts off the water temporarily without changing your hot/cold settings. You get in, get wet and warm, then reach up and turn the valve to shut off the flow. You soap up (without having to step away from the flow area), then turn on the valve and finish.
This simple device only costs $5 to $10 and can save between 50% to 75% of your hot water use, with little inconvenience. If you cut your water usage in half, your shut-off valve will pay for itself in about a month. This does not include the environmental savings of the energy required to move and treat the water, which is significant.