For those starting to think about upgrading to SQL 2012, or for SQL 2008 sites, should I upgrade to SQL 2008 R2 or SQL 2012, you will find the SQL Server Upgrade Advisor an excellent first step and rewarding toe in the water experience.
A link to the upgrade advisor can be reached here that includes the links to download the tool SQL Server 2008 R2 Upgrade Advisor Link – ordinarily this would be available in the SQL 2008 R2 feature pack.
Running the upgrade advisor is simple and allows you to select and analyse only the components you are thinking about upgrading. For example if you only want to upgrade Reporting Services, then only select the Reporting Services option. Keep in mind, for Reporting Services, you must install and run the tool locally on the Reporting Services server, whereas for the other components (SQL Server, Analysis Services, etc) you can analyse from a client workstation that has upgrade advisor installed. Any issues can be viewed later using the same upgrade Advisor tool but using the Report Viewer option.
The link to the current SQL 2012 Release Candidate Upgrade Advisor is here SQL Server 2012 Upgrade Advisor Link.
I also recommend running the SQL Server Best Practices Analyser to help identify risk areas that might be better sorted out before you plan to do the upgrade. The link to the Best Practices Analyser can be found here SQL Server 2008 R2 Best Practices Analyser Link. BPA also performs some O.S. level checks so is recommended to install and run on the actual SQL Server you intend to analyse. It is also works on SQL 2008 instances.
Currently, the SQL 2012 Best Practices Analyser defers to the SQL 2008 R2 version SQL Server 2012 Upgrade Quick Sheet.
Hope this helps.