startup on your os 9 cd...there should be a utilities folder, in there should be an app called HD setup utility. Use select your hard drive you want to partition...there is either a partition button or you need to just hit format. (i haven't used the program in a couple years and i'm at work using a wintel machine so i can't check) Anyway, then you can select how big the partitions are to be. Doing it this way will delete everything on your hd though. There are programs out there that will attempt to resize your partitions without deleting stuff. From my experience these aren't worth your time to get. They work, but from my experience they screw up 1/4 of the time, so you'd be stupid not to back things up, which is the biggest pain in the ass, so if you're going to back things up you might as well just start from scratch
I wanted to install LinuxPPC a year ago and I had to partition.
If youare going to partition, back up but make sure that you
have ample time available.
Backing up takes a looooooong time.