SQL queries are slow, what do I check?

You some day will face the following problem: your queries have turn out very slow, having SQL Server so many components, you need to start checking some basic points. You can start checking out the following DMV:

Sys.dm_exec_requests
Sys.dm_tran_active_transactions
Sys.dm_os_wait_stats
Sys.dm_exec_query_stats

These DMV will give an idea where all the server resources going. If you want you can focus on dm_os_wait_stats that will give an idea to start the diagnostics to find the performance bottleneck.

Regards,

Eduardo Castro Martinez
Microsoft SQL Server MVP