Pre-Stage CNO for DAG (Exchange 2013)

Overview

Before creating a DAG in Exchange 2013, you have to "Pre-Stage" the Cluster Name Object (CNO) in Active Directory.

Down and Dirty

Create a computer object that matches the name of the DAG you want to create.
Disable the computer object.
Set the security permissions for the "Exchange Trusted Subsystem" to Full Control.

References

http://technet.microsoft.com/en-us/library/ff367878(v=exchg.150).aspx