I've been testing Window Server 2012 via the "Early Experts" class, which is a very cool class, and experienced this very informative, super user-friendly TechNet how-to article on Group Policy. I'm not a GP guy. What I mean by that is that my job doesn't require a deep understanding of GP, only a foundational level understanding of GP, so I don't know the really cool things you can do with GP for your network(s). After going through this how-to for Server 2012 I now understand some deeper things about GP.
The how-to is for Server 2003, but it works for Server 2012 at least for the part we are at in Administering GP.
Check it out here.
I highly suggest going through, at your own pace, the Windows Server 2012 Early Experts challenge.