High SOS_SCHEDULER_YIELD and Signal Waits
Recent expensive queries in the Activity Monitor in SSMS should be your first stop. 

For more information grab SP_Whoisactive and find Glenn Berry's diagnostic queries which will help you a lot. The exact query depends on the version of SQLServer but this should be a start.

SELECT TOP(50)
  creation_time
 ,last_execution_time
 ,(total_worker_time+0.0)/1000 AS total_worker_time
 ,(total_worker_time+0.0)/(execution_count*1000) AS [AvgCPUTime]
 ,execution_count
 ,st.text
FROM sys.dm_exec_query_stats  qs
CROSS APPLY sys.dm_exec_sql_text(sql_handle) st
 WHERE total_worker_time &gt; 0
ORDER BY total_worker_time DESC