"SQL Server-related performance problems come up regularly and diagnosing and solving them can be difficult and time consuming. Read SQL Server MVP Jonathan Kehayias’ Troubleshooting SQL Server: A Guide for the Accidental DBA for descriptions of the most common issues and practical solutions to fix them quickly and accurately."
Please go to http://www.red-gate.com/products/dba/sql-monitor/entrypage/tame-unruly-sql-servers-ebook
RedGate produce some superb tools for SQL Server. Jonathan's book is excellent - I commend it to all SQL DBA and developers.