Tip: Use search in System Preferences
Have you ever wanted to change a system preference but you couldn’t remember where it is? Say you want to assign a password to your screensaver—where is it? You check in the obvious place, the Screen Saver panel, but it’s not there.
When this happens, remember to click in the search field in the upper-right corner of the System Preferences window, and type screen saver.
Oh, there it is—in Security, of course!

In Leopard, you can use Spotlight to do the same thing:
