I just completed a dual-boot install on a new 12" Powerbook. Many of the
available HOWTOs are out-of-date and did not work for me. What did work:
1. Put in the OS X install disc and use the Disk Utility to partition
the drive into two partitions, putting OS X on the second partition.
2. No other Debian Install method worked for me except using the
debian-installer rc2. I chose the net install image here:
(the reasons included that the Mar 8 2005 sarge discs did not recognize
the ATA 100 hard disk and all the methods involving copying yaboot files
and .bin files into the first partition didn't work either sometimes for
the same reason sometimes for other reasons.)
3. The installer will guide you through partitioning, but basically
you'll make an 820k newworld boot partition near the front, a swap
partition, and a root partition (which can be subdivided some more if
you like). I chose not to mess with the crufty "free space" partitions
that Mac leaves behind because some say they're important while others
say they aren't. I didn't want to have to start over for 128 megs.
4. I don't have sound working, the new trackpads are USB and not yet
supported, and, of course, the airport extreme doesn't work.
The Debian net install was very smooth though. Try it.