Allegedly, on or about 25 September 2013, Richard Vickery sent:
I forget how to edit Grub: I thought editing was in /boot/grub and tried to vi grub.cfg finding an empty page...
That was the old version. Now, the /etc/default/grub file, and /etc/grub.d/ files are used for generating the grub config file.
But that wasn't what Joe was talking about. Rather than edit the configuration files, he suggested temporarily changing the options that grub will use as it boots. Start booting, pick a kernel to boot from, but choose the edit rather than boot option. Then change the kernal commands line it'll boot from.