I published this lists few years ago. But I think is still very relevant, that is why I decided to review it and put it on the top again. This is by far my preferred migration method.

1. Secure mail routing between on-premises and Exchange Online organizations. Require TLS authentication
2. A unified global address list (GAL), also called a “shared address book.”
3. Free/busy and calendar sharing will continue working between on-premises and Exchange Online.
4. Centralized control of inbound and outbound mail flow. Costumer can configure all inbound and outbound Exchange Online messages to be routed through the on-premises Exchange organization.
5. A single Microsoft Office Outlook Web App URL for both the on-premises and Exchange Online organizations. User will continue visiting OWA and they will get redirected from there to the cloud if needed.
6. The ability to move existing on-premises mailboxes to the Exchange Online organization without interrupting the end-user.
7. Exchange Online mailboxes can also be moved back to the on-premises organization if needed.
8. Centralized mailbox management (Cloud and on-premises mailboxes) using the on-premises Exchange admin center (EAC).
9. Message tracking, MailTips, and multi-mailbox search between on-premises and Exchange Online organizations will continue working
10. No need to reconfigure the end-users’ profile. User will keep rules, signature and .n2k files in their outlook.