how do I do a dual boot in Mac? Should I want to go into OSX how do I tell it to do so?
If you have your OSX CD set or DVD, I recommend that you start fresh by partitioning your hard drive into 2 partitions: 1 partition for OSX (just enough to hold the OS itself and perhaps half a dozen of your frequently-used 3rd party apps) and 1 other partition for MintPPC (make sure you mark that partition as unused space in OSX's disk utility). Bear in mind that this will erase EVERYTHING that's on your drive right now... so you should make backups before you try a dual-boot configuration.
Then, install OSX on one partition. Reboot into OSX and do whatever tweaking/cleanup you usually do, like registering with Apple (hehehe), configuring your network settings, etc.
After all of that, you can install MintPPC. Just make sure that during the process of installing the base Debian (you know... the stuff with the blue screen), you pay particular attention to the part where you tell Linux to use the largest free space available....... and in this case, it should be able to detect the empty partition you set up earlier. After that, just proceed with the installation as you did last time.
Make sure you get your xorg.conf downloaded and installed and add yourself to the "sudoers" file so you can fine-tune your MintPPC installation once you get into the GUI. There are proceedures for that on this forum... they're easy to find.
And so each time you reboot, you'll be able to choose from a time-delayed list which OS you want to boot into.
This should work even with a triple-boot setup... like if you added Mac OS 9 into the mix.... but that's probably more trouble than it's worth... I can't remember where I read it, but there are/were people who said that Yaboot keeps knocking OS 9 off the list entirely after each reboot.