Upgrading a Windows Server Failover Cluster to the next version of Windows Server is not one of the easies processes compared to other server roles. When I was ready to move my cluster to 2012 I looked online for the best resource that I could find to help with the transition. During my search I found this MSDN article that is as close to a step-by-step that I could find. There are two different ways to move from 2008 R2 to 2012: Windows Server 2012 Failover Cluster Migration Wizard or System Center 2012 Virtual Machine Manager with Service Pack 1. I used the Migration Wizard. In order to use the Migration Wizard, you need to create a new cluster. I had six nodes running my cluster, to create the new cluster I evicted half and created a new 2012 cluster with them. I then connected my SAN via iSCSI to my new cluster while connected to my old cluster. Next I ran the migration wizard to copy the configuration over to the new cluster. After this step, I took the Virtual Machines and the shared storage offline (in that order) in Failover Cluster Management in the 2008 R2 cluster. As soon as I did this the storage then appeared in the 2012 management window and I put them online. Now I am running on Windows Server 2012.
When you decide to make the move to Windows Server 2012 for you Active Directory Federation Services server, there are a few things to keep in mind. First is the migration process for ADFS on Windows Server 2008 R2 to Windows Server 2012. The second one is if you as an organization are using ADFS with Office 365. If you are using Office 365, then the relying trust can not be added back manually like the first document says. Office 365 automatically created this when running the federation command in PowerShell when you originally federated the domain to Office 365. You would need to repair the relying trust with PowerShell. Follow these instructions from Microsoft.