Ensure that an audit has been performed on all services so that servers that required IIS have the service reenabled after migration.
Since prototype phases of a project are essential for testing design assumptions for a Windows Server migration or implementation, create a production domain controller and subsequently isolate it in the lab for testing.
Test the hardware compatibility of all servers which will be directly upgraded to Windows Server 2008 R2 against the Hardware Compatibility List published by Microsoft.
Remember that that Windows Server 2008 R2 is available only as a 64-bit OS when developing your migration plans – 32-bit hardware will have to be decommissioned.
Since the decision to raise the forest or domain functional levels is not reversible, make sure that there is no additional need to add Windows Server 2003 or Windows Server 2008 domain controllers anywhere in the forest and that there aren’t any other compatibility issues before performing this procedure.
If the server(s) which hold the OM roles are not directly upgraded to Windows Server 2008 R2 but instead will be retired, move these OM roles over to another server.
When using ADMT, first migrate the groups into a new domain to keep users’ group membership intact.
Use the Windows Server Migration Tools for migrating server roles to Windows Server 2008 R2.