On my Dell Inspiron 14z I just press F12 to get the boot menu, or F2 to head straight into firmware. I think there's a very very tiny window for pressing the shortcut key but it's there. Once those tiny dots start spinning you're out.
Once in there you can disable Secure Boot and enable Legacy boot devices to get good ol' BIOS behaviour. I don't know if this is true of all Windows 8 machines but it seems Secure Boot must be disabled or there's no option to boot to anything but Windows or network
You can bypass Fast Boot
Once in there you can disable Secure Boot and enable Legacy boot devices to get good ol' BIOS behaviour. I don't know if this is true of all Windows 8 machines but it seems Secure Boot must be disabled or there's no option to boot to anything but Windows or network