This article describes the exact steps to successfully upgrade SCCM 2012 to SP1. We had 2012 up and running and were in the process of slowly replacing our 2007 environment, one site at a time. We've since finished the migration and have had no issues with 2012. Please update or elaborate any steps you think need it.

Environment:
  • Windows Server 2008 R2 Standard Service Pack 1
  • SQL Server 2008 R2
  • System Center Configuration Manager 2012 (version 5.00.7711.0000)
  • Existing SCCM 2007 environment still in production
Links:
Instructions:
  1. Install Operating System updates from Windows Update
  2. Install Mgmt Framework 3 for PowerShell access.
  3. Uninstall Windows Automated Installation Kit
  4. Install Windows Assessment and Deployment Kit
  5. Upgrade WSUS using KB2734608.
  6. Make a full SCCM database back up
  7.  Upgrade server to 16gb ram. (adjust for your environment/load)
  8. Set SQL min memory to 8590mb, max to 10738mb.
  9. Stop data gathering from SCCM 07 environment.
    1. SCCM Console
    2. Administration
    3. Migration
    4. Source Hierarchy
    5. Right-click IDC and stop gathering data.
  10. Export all default collections just in case.
  11. Start the upgrade. Monitor C:\ConfigMgrSetup.log.
  12. Verify new version 5.0.7804.1000 is installed.
  13. Re-distribute client package to DPs
  14. Push client to all existing clients again, selecting "Always install"
  15. Update Config Mgr console package
  16. Recreate OSD media with the new client installer