Other resources

• Brent Ozar
  This guy provides one of the best packages for identifying and solving performance issues in your SQL Server.
  He also writes blogs on optimization and creates very easy-to-understand videos on the subject.
  You´ll find him here Brent Ozar.
  
  
• Erik Darling
  Writes a lot of valuable content in his blog about optimizing SQL Server.
  He also has a package of SQL scripts that is a must-have for any DBA looking for a smoother workday.
  Check it out here Erik Darling.
  

Make sure to follow these guys, read and watch everything they produce.