As discussed on Mac Geek Gab 345, listener Bob sends in a great tip about using boot modifier keys on a Bluetooth keyboard.  Boot modifier keys are those keys or key combinations that are held down when starting a Mac to select certain options.  For example, holding down Option will bring up the boot menu, allowing the user to choose a drive to boot from; holding Shift will start the Mac in Safe Mode; holding C will start the computer from a bootable optical disc; and so on.  Krypted.com maintains a great summary of the different modifier keys.

Press your boot modifier keys after the chime, but before the spinning gear appears.

One problem is that these boot modifiers seem not to work with Bluetooth keyboards, as many users who hold down the modifier keys immediately at startup find that the Mac boots up normally, ignoring the modifiers.  The solution is simple: wait to press the keys until you hear the startup chime, but before you see the spinning gear at boot.  This allows the Mac to load the appropriate bluetooth drivers so that it can see the keyboard, but is early enough in the boot process that the keys aren’t ignored.

Thanks, Bob, for the great tip!