Here is the May 2013 version of my SQL Server 2012 Diagnostic Information Queries, with some minor tweaks and improvements to several of the existing queries. I have improved the formatting of the results to make many of the queries easier to read and interpret, especially for the missing index queries.
To go with it is an updated, blank 2012 results spreadsheet, where the tabs in the spreadsheet are labeled and in the same order as the queries. The idea is that you can run these queries one by one, click on the top left square of the results grid, and then right-click and select “Copy with Headers” to select and copy the results of the query and then paste them into the matching tab of the results spreadsheet.
Many of these queries only work on SQL Server 2012, although some will work on older versions of SQL Server. If you are using an older version of SQL Server, you should use the version of my diagnostic queries for that version of SQL Server.