0. create an account on the macos9lives.com forum
1. burn this disc & put it in the mac
    http://macos9lives.com/smforum/index.php/topic,2143.0.html
2. reboot the powerbook into Open Firmware by holding Command + Option + O + F from powered off.
3. Enter the following, pressing return after each line (except lines with <> or starting with //)
nvedit
// masquerade as another cpu
dev /cpus/PowerPC,G4@0
80010201 encode-int " cpu-version" property
// disable sound device, os9 doesn't like it
dev /pci@F2000000/mac-io/i2s/i2s-a
" screamer" encode-string " compatible" property
<Ctrl-C>
nvstore
setenv use-nvramrc? true
reset-all
4. The computer will reboot immediately after reset-all; hold the option key to bring up the boot device picker
5. Wait for the waiting cursor to go away, click the MacOS9Lives disc and then immediately start holding the shift key.
6. You can let go of Shift once you see the text "Extensions Off"
6. When OS9 boots, install to your HDD
7. Remove the "Multiprocessing" folder from HD > System Folder > Extensions



! if something goes wrong in Open Firmware, reset NVRAM/PRAM with Command+Option+P+R when booting

Sources
https://www.thinkclassic.org/viewtopic.php?pid=4889#p4889
http://macos9lives.com/smforum/index.php/topic,2143.0.html

    

    maybe add this too 

    from https://www.thinkclassic.org/viewtopic.php?pid=12113#p12113


to force booting from USB on the right side:
devalias ud /pci@f2000000/usb@1b,1/disk@1
dir ud:1,\
boot ud:1,\System%20Folder\Mac%20OS%20ROM