I wrote the first version of this on 9/13/2008. I was looking for it 11/21/2020 and decided to see if I could update it a bit in advance of going from Mojave to macOS Big Sur sometime in 2021 (I skipped Catalina entirely). I'm also experimenting with a revised publication date in Blogger.
For my own amusement I kept the original below. Here's what I do now for macOS updates:
- Make a fresh Aperture backup (still using it!) from within Aperture.
- Test both my Carbon Copy Cloner and Time Machine backups including a test file restore. I create two CCC clones and take one off-site. I don't usually make bootable clones but I do this time.
- Remove my backup drives.
- Disconnect everything.
- Reset SMC, reset NVRAM.
- Run hardware diagnostics, Onyx cleanup, and Same Mode boot.
- Turn off Time Machine backup.
- Update OS.
- Login to each user account on the machine and get iCloud working, check that Google services are connected (Mail, etc), run Notes, Contacts, Mail, etc.
- Do backup to fresh carbon copy cloner drive. Note Time Machine is still off.
After a day or so I have to decide what to do with Time Machine. I usually start over with a fresh TM backup rather than try to continue with the old one. My primary backup is CCC.
The original post from 9/13/2008
I prefer an OS update to petting a rabid wolf or getting a kidney transplant. Even so, they're not my favorite things. It was clear early on that Apple had botched 10.5 - a prelude to the MobileMe fiasco and the iPhone OS 2.0 fender bender. So I waited to 10.5.3 before updating our non-critical MacBook. That didn't go all that well; I'm still having problems.
On the other hand there's a lot to like about 10.5, and I imagine I know what to watch for.
After lots of experience with 10.5.4, I was read to risk an update to very important machine -- our trouble free PPC iMac G5 running10.4.11.
It's the procedure I follow with all major OS updates. I do all the work through my admin account.
- Check the backups are working so I know I have a current backup of data. I like to do a test restore of randomly selected file.
- Have another machine available in case the update runs into problems -- you may need Google.
- Don't do the OS update on a desktop machine during bad weather. This is a bad time to have a power failure. Make sure you can't accidentally pull a plug or turn off the power. (I once bricked a peripheral by hitting a power switch with my foot.)
- Do a safe boot to clean up the system and verify the drive.
- Disconnect all USB hubs and all firewire devices. Attach only an Apple keyboard and an Apple mouse.
- Pull the network cable (see below). You can plug it in when you need to get software updates. Nowadays there are all sorts of things a partly updated machine can destroy if it can get a the net.
- Restart then remove Preference Panes from admin account (ctrl-click then delete in preference view). Review and remove suspicious login items. Use Spotlight to find all apps or utilities with a date prior to 2004 - remove any that aren't needed.
- Uninstall known bad actors. I know, for example, that my copy of Missing Sync for Palm OS won't work with 10.5. I don't need it any more, so time to use the uninstaller. Remove Retrospect's client if present, that will need to be reinstalled.
- Turn off sync services, such as Spanning Sync. Don't turn them on again until you've run iCal, Address Book, mail, etc for the first time. I recommend turning off everything related to synchronization, including .Mac/MobileMe, anything in iTunes, any add-on services. To be extra sure, pull the network cable durign the update. Don't allow the machine to access the net without your control.
- I've already removed the evil Adobe Acrobat Reader and RealAudio.
- Copy the 10.5.4 Combo Updater to the desktop. I don't want to run 10.5.2 a moment longer than necessary. Confirm I have plenty of free drive space left.
- Review Mac OS X 10.4, 10.5: About installation options so I don't miss the 'Archive and Install' option  . (Made that mistake before!)
- Insert DVD and click the install button.
- Go walk the dogs, do the dishes, etc. Just the DVD verification takes an age and a half. (Yes, you can skip the verification. I prefer to let it run.) The update should proceed without any questions, so you can let it go.
- After the upgrade and reboot it can take a long time for the admin account to come up. Be patient.
- Restart again (to let caches be build properly) then apply the 10.5.4 compo updater. The machine will restart.
- Check all login items for all users. There's a bug in the 10.5.2 Archive and Install procedure that can cause login items to be applied across user accounts.
- Check for other updates. I was surprised I had to install iTunes 8 again -- it had been installed earlier. I imagine if I hadn't done this, and I'd tried to sync to my iPhone, the heavens would have fallen. You have to keep checking until no new updates are found.
- Run iCal and Address Book. Anyone else notice that 10.5 Address Book backup is under the export/archive menu now? Back 'em both up before any iPhones sync.
- Enable Spanning Sync and do an iCal sync with gCal.
- Run Keychain Access and Keychain First Aid.
- Run any app that iTunes works with or that intersects with the iPhone.
- Cycle through all accounts, looking for obvious trouble.
- Hook up the peripherals, download drivers for the MacAlly keyboard, etc etc.
- Expect Spotlight to suck CPU and drive the fan until the search indices are rebuilt. Let it run overnight.
- The long recovery begins.
- MobileMe didn't appear in software update, so it was only when I went to the old .Mac preference panel that I was asked to update to MobileMe. This might have caused some problems if I'd installed MobileMe.
- iTunes regressed to an earlier version. I had to update to iTunes 8 again. This would have caused serious problems if I'd missed this.
- Spanning Sync keeps telling me its deleting appointments from Google Calendar, but it doesn't say what it's deleting. I don't know why this is happening.
- The update resurrected a number of old apps and login items that I thought were long gone. They're reaking havoc on my syncs.
 Select this option if you want to install a "fresh" system on your computer. This type of installation moves existing System files to a folder named Previous System, then installs a new copy of Mac OS X. You cannot start up your computer using the Previous System folder. Archive and Install installations require the largest amount of available disk space because you need to have room to preserve your existing System and the new one you are installing. This is a good choice if you've already backed up your important files and are trying to resolve an existing issue. Mac OS X-installed applications, such as Address Book and Safari, are archived, and new versions are installed in the Applications folder. Some applications, plug-ins, and other software may have to be reinstalled after an “Archive and Install.” Fonts that were installed in the Fonts folder in the top-level Library folder can be installed in your new system by copying them from the Previous System folder.