We often get the question, "When I'm turning my computer off, should I turn off the power bar, or should I turn off the switches on each piece of equipment and the power bar?"
First, if you want more information on power bars, see this article "Power Bars."
When you are shutting down your computer, make sure you tell it first, that you are going to shut down (on a computer with Microsoft Windows, this means click on Start, click on Shut Down or Turn Off (which ever your computer has), and click on Ok or Yes).
In our classroom, after we do the Shut Down command, we then have the students turn off every power switch (on each piece of equipment), and then turn off the power bar. This is so the students learn where every switch is.
But at home, on my own computer, after I tell it that I am going to shut down, I just switch off the power bar. I leave every switch (on each piece of equipment), in the "on" state (there is no power in any piece of equipment, because the power bar is off, but the switches are in their "on" position). This way I only have to turn one switch off, not a whole bunch of switches, and there is no chance of missing one of the switches. Usually with this method, you will have to turn the computer switch back on later, as well as the power bar, but the other pieces of equipment (for example, the monitor or printer) will come on when you turn the power bar on.
On the other hand, sometimes people have difficulty reaching the power bar (for example, if it is down under their desk, on the floor), so they just turn off the power switches on each device. Some people have fewer devices in their computer systems, and also, most new computers shut their own computer power off when you tell them to do the Shut Down command, so you would only have to shut down the monitor, and any other devices you turned on, like a printer or scanner, with this method.
As far as protecting your equipment goes, it doesn't make a noticeable difference in practice, with either method, so it is more a question of which advantages you want. I personally prefer to just switch the power bar off, but it's up to you.
Note: If you are using someone else's computer, always ask them how they want it shut down (especially if you are in an office - they may even want it left on for maintenance, or so others can access it over a network).