You'd be amazed at how often a simple reboot (that is, shutting down and restarting your Mac) can cure a temporary problem. For example, this can fix the occasional lockup in Mac OS X or a keyboard that's not responding because of a power failure. If possible, make sure that you first close any open documents or you might lose unsaved work. When troubleshooting, always do a shutdown instead of simply restarting the computer, because when Mac OS X shuts down, all the hardware components that make up your system are reset.

If your Mac is locked up tight and you can't use the Shut Down command from the Apple menu, you have two choices. First, press and hold the Power button on your Mac for a few seconds, which turns the computer off. If this doesn't work — and, from time to time, it actually doesn't — you'll have to physically pull the power cord from the wall (or turn off the surge suppressor, if you're using one). However, save this last option as absolutely the last resort.