I had a question on I.M. today on how to set the default menuentry to boot that one wants, when there is no menu.lst file.
Simple, m'dears, see line 12 on that pastebin. The first menuentry is 0, the second is 1, the third is 2, and so on and so forth. The line originally was set to "0" - this person wanted the third menuentry to boot. So, I showed them how to change that in that line. The line now reads: 'set default="2"'. They rebooted to confirm it was working, and it was.
Edited for filename correction
Edited Dec. 18, 2010 for Grub version clarification. This is for Grub1 - although it may possibly be helpful with Grub2 as well.