Go
here. (Question 9 should be of help)
The instructions are for Mandrake 8.2, but I think they should still be good. Also the current issue of Linux Format has detail on this (page 24 and 25) but effectively it mirrors what's on the Mandrake site.
You could also try going to
the Yellow Dog Linux site and looking at their installation guides.
I have read that Linux on Mac flies - but have no personal experience of it.