I just installed Windows Server 2012, and while I see and read about a new deduplication feature, the Server Manager keeps reporting empty fields in the columns for deduplication rate and savings. How do I get the server to start looking for deduplication opportunities?
You need to install, enable, and configure the dedupe features.
Since there is overhead associated with deduplication, and there are scrubbing and other jobs that need to be scheduled, it's not automagically enabled on a default install.
You can do this from the GUI, or using PowerShell:
Please note that the commands listed above are the bare minimum necessary to turn dedupe on. If you want to use this in production, read the entire link and understand all of the other components involved and configure them as necessary.