Getting into the rEFIt menu
If you have installed rEFIt on your Mac OS X volume, it will be loaded automatically when the Mac starts up.
With rEFIt installed on a separate volume (internal or external) or on a CD, hold down the “Option” key while the Mac starts up. That activates the built-in boot menu, where you’ll see an icon labeled “rEFIt”. Choose it with the arrow keys and hit Return, and the rEFIt menu will be loaded.
You can configure your Mac to automatically start the rEFIt menu even when it is installed on a separate volume. Just use “enable-always.sh” instead of “enable.sh”.