MacFixIt has posted guidelines “aimed at reducing common issues that occur during as a result of the [Mac OS X Leopard] upgrade process, including pre-update preparation, proper installation, and post-update maintenance.”
Topics covered include:
• Backing up your data
• Preparing your startup disk
• Other pre-update precautions:
– Make sure all devices are synchronized prior to updating
– Disconnect all external devices, update firmware
• Install options:
– Archive and Install
– Erase and Install
• Upgrade applications to Leopard-ready versions, if they are available
• Disable plug-ins and other application add-ons (or upgrade them)
• Check for, and delete, corrupt .plist files
• Do not run DiskWarrior and other directory utilities after updating
Full article here.
See also, “Installing Leopard to an external firewire drive,” here.