If you don't have a solar geyser then you need to concentrate on:
-> using less hot water (shower [not bath] using a low‑flow shower head),
-> reducing the temperature of your geyser's thermostat, and
-> reducing the heat loss from the hot water pipes (insulate them)
(and not on turning your geyser off).
If you do have a solar geyser then you need to
-> do all of the above (for no solar geyser)
-> as well as installing a time switch.
But, where is that thermostat that I keep referring to, and how do I adjust it so that the water is not so hot?
The geyser's thermostat is on the geyser, inside a protective enclosure (see Figure 1 below).
Figure 1: Geyser with Thermostat enclosure (closed)
To get to it, you need to:
1) turn off the electricity supply to the geyser (to be 100% safe, turn off all the switches on your electrical distribution board)
2) find the geyser - usually in the roof (Note: if you are climbing into your roof, then make sure that you step on the rafters (not on the ceiling board) otherwise you will fall through the ceiling and onto the floor!), then
3) open the protective covering
4) using a small flat screw driver, turn the thermostat setting screw to a colder setting [usually, clockwise] (in Figure 2 below, the setting is 40 degrees Celsius)
Figure 2: Thermostat enclosure open, and set to 40 degrees Celsius
Note: the thermostat settings are not exact and you might need to visit your geyser more than once.
Update on 16June2010:
Watch out or, at least, be aware: #WTF Geyser's element has just blown <3 years after installation... 5 year geyser warranty, but only 3 months on the element! #FFS #RipOff