Can you please tell more about the migration - meaning are you migrating from On premise to Cloud like AWS. How big your content is and also the customization - as the strategy needs to be decided accordingly.
Mainly the content migration, DB migration and the customized war strategy needs to be decided.
The first major step - Backup
a) Content in alf_data has to copied to destination via sync/tool or Snowball if content is large volume.
b) Data in DB has to be copied to destination DB.
c) wars needs to be applied at destination server
d) configurations for the custom modules/amps need to be applied as per the destination env, smtp settings etc.