Use the device maker's update system
Avoid update packages or instructions from unknown third parties.
Check available storage
Large updates may need temporary working space.
Confirm important data is backed up
Google and Apple both provide current official backup systems for supported devices.
Allow time for post-update settling
Indexing, app updates and background tasks can temporarily affect performance after a major update.
General consumer technology information only. Interfaces and menu names change. Before resets, reinstalls, storage changes or other major actions, verify that important data is backed up and use current manufacturer/service-provider instructions.