Ignore all the guides out there that talk about Refit.  Just pretend it’s a PC.

  1. boot from Linux CD
  2. Clear the partition table (using Gparted and create a “MSDOS” table)
  3. Install Linux (normal partition stuff applies–must be marked “boot”)
  4. there’s a “bless” command to run from the Mac OS X install cd that will make it boot more quickly