I wish the search on the downloads site at Microsoft worked better.  You can even input the name or title of this one and still no luck.....

You can download "Troubleshooting Performance Problems in SQL Server 2008" from the Microsoft Download Center. 

It is a 63 (a few less once you subtract table of contents, etc) page document packed with a lot of good information.  For those who are looking for a troubleshooting methodology, this document covers the basics and how to get started.

It also covers using three of the new DMVs added in SQL 2008 and how to use them:

• sys.dm_os_memory_brokers
• sys.dm_os_memory_nodes
• sys.dm_exec_procedure_stats