https://social.technet.microsoft.com/wiki/contents/articles/43908.active-directory-migration-checklist.aspx

-Create the network connections between the Source and Target domains
What Routers?
-Setup DNS
-Setup 2 Way Trust
What Applications Need AD Auth ?
File Server Migration?
Migrate GPO
-Installing the ADMT software\Installing the Password Migration Service
-USMT Profiles -https://github.com/nickrod518/Migrate-WindowsUserProfile


365
– Identity for email?