For everyday users, it may be easiest to just set the energy saver feature (such as monitor off after 1 hour and automatic power shut down in 2 hours). For me though, I don't use the power-save feature. If my computer has to stay on, it's staying on for a reason.
Instead, I have everything hooked up to a power strip that is controlled by a wall light switch. This includes my modem and router; two items that often gets overlooked and is left on all the time.
So, when I come home, I turn everything on with a flick of a switch. When I go to bed, I turn everything off. When I'm home and not planning to use it soon, I just put the computer on standby. Locks the computer and saves energy at the same time. Recovery is also much quicker than a cold boot.
Power saving also depends on what kind of hardware you have. If you have a fancy computer with a larger monitor, it will draw more power (sometimes as much as a microwave left running) than it will if you just have a small laptop or something similar.
Lastly, I don't really know what my power saving is. While power saving is nice, it's not actually the primary reason for my setup. You see, I'm a security freak....
