Here you go. Some steps can be skipped if not relevant to your system.
Follow these instructions step by step to prepare a Mac for sale:
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First, back up the data:
1. Shut down all Virtual PCs. They cannot be in their "fast saved" state. They must be shut down from inside Windows.
2. Clone to an external drive using using Restore option of Disk Utility.
Next, prepare the machine for the new buyer:
3. Deauthorize the computer in iTunes! Deauthorize both iTunes and Audible accounts.
4. Remove Open Firmware passwords
5. Turn the brightness full up and volume nearly so.
Install a fresh OS:
6. Insert the OS X install CD/DVD.
7. Restart the computer while holding down the C key to boot from the CD/DVD.
8. Run Disk Utility from the file menu and erase the internal hard drive (optionally zero all data).
9. Install OS X.
10. Reboot the computer.
11. From the welcome screen, you can skip the registration step by typing command-Q.
12. When prompted, create an account (it will be an admin account).
13. From your new admin account, configure networking.
14. Then use Software Update to bring your system and all of it's applications up to date.
15. From Disk Utility, repair permissions on the new volume.
Now delete the account you just created:
16. Boot from a different volume (e.g. a firewire drive, if available)
17. Clean up the image using the following terminal commands:
prompt> rm /Volumes/<imagevol>/var/db/BootCache.playlist
prompt> rm /Volumes/<imagevol>/var/db/volinfo.database
prompt> rm -r /Volumes/<imagevol>/var/vm/swap*
18. Now you can get rid of the admin account you used to set up the machine Use the terminal:
prompt> nicl -raw /Volumes/<imagevol>/var/db/netinfo/local.nidb -delete /users/<admin>
prompt> rm -r /Volumes/<imagevol>/Users/<admin>
prompt> rm /Volumes/<imagevol>/var/db/.AppleSetupDone
19. Shut down and ship it to your buyer. When they get it, it will boot to the Welcome screen just like a factory Mac, except that it's better because it's completely up to date.
