If you are new to DBA career or did not spend enough time on SQL Server Query Tuning skills then here is a right stuff to start with. As licensing models are changing and adding hardware also associates the licensing costs along with the hardware cost itself so fine tuning the queries and procedures is a required skill for DBAs.
You can download about 6 hours of training videos related to SQL Server Query Tuning skills. Videos are equipped with theory and demos side by side. These training videos are prepared for SQL Sentry by