The steps involved in the actual migration process will differ, depending on the option chosen.
Effectively they will follow the same basic pattern:
Creating users' accounts
Activating Exchange Online mailboxes
Migrating mailbox content
Generally the Mail eXchange (MX) record is cut over after the completion of a successful mailbox migration however some administrators prefer to do this beforehand to ensure that no new mail items are left behind.
However, the key to a successful migration is not the actual mailbox content migration itself, it is the planning and preparation.