Since we are in the middle of May 2011, I thought was was time to update my SQL Server 2008 Diagnostic Information Queries. These are very similar to the April 2011 version except for one new query at the end of the set.
You can click on the link above to download the queries from Dropbox. What I always recommend is that you run each query separately, after you read the instructions and comments on how to interpret the results. The first half of the queries focus on your SQL Server instance, while the second half focuses on a specific SQL Server database on that instance. That means you want to make sure you are in the context of the right database when you run the database specific queries (not master).
This set of queries will work on both SQL Server 2008 and SQL Server 2008 R2. There is a separate set of queries available for SQL Server 2005, and a separate set available for SQL Server Denali.
I also recommend that you download the matching query results spreadsheet, so that you can copy and paste the results for each query into it, for later analysis. This makes the results much easier to interpret, and lets you keep a record of changes over time.