I was trying to determine whether I had put all of my tables on the correct filegroup and I wanted to list this. I came up with the following query to quickly list all the needed information.

SELECT o.Name as 'Table Name', g.GroupName
FROM sysobjects o
JOIN sysindexes i on i.id = o.id
JOIN sysfilegroups g on g.groupid = i.groupid

A lot of people tend to use DBCC FREEPROCCACHE when they are performance testing procedures. This is obviously a very good habit, however, when sharing a server with other databases you are clearing the cache for all databases. You can prevent this by using DBCC FLUSHPROCINDB(dbid) which only clears the cache for a specific database.

Found this old but yet very useful article in SQL Server Magazine (InstantDoc 40925).
It is an in depth study of DBCC SQLPERF (WAITSTATS) with a lot of information on what to monitor.

There are a couple of interesting formulas in the article that came to my attention.

Initial Compiles(%) = (SQL Compilations/sec - SQL Recompilations/sec) / Batch Requests/sec
Plan Reuse (%) = (Batch Requests/sec - Initial Compiles/sec) / Batch Requests/sec

To determine the optimal Packet Size use the following formula:
Average Number of Bytes per packet = Bytes Total/sec / Packets/sec