The two books below in my signature can help with query tuning. I also wrote part of an introductory book called Begginning SQL Server 2012 Administration. After that, all the free books available from Red Gate are a priceless resource.
"The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood"
- Theodore Roosevelt
Author of:
SQL Server Execution Plans
SQL Server Query Performance Tuning