Build an inventory
Record installed extensions and their purpose. Identify unused items, custom modifications and components whose vendor support is uncertain.
Confirm the supported path
Read the relevant migration guidance and each dependency's compatibility information. Do not assume a sequence of version changes is safe because the administration screen offers an update.
Rehearse real journeys
Check content, URLs, accounts, forms and integrations on an isolated copy. Ensure that test email or payment connections cannot accidentally create real effects.
Prepare the release decision
Take a current backup and establish how to restore it. Agree a content freeze or final synchronization, a cutover window and the conditions that would trigger rollback.