How to troubleshoot the performance of Ad-Hoc queries in SQL Server

How to troubleshoot the performance of Ad-Hoc queries in SQL Server (Knowledgebase Article)
This article describes how to troubleshoot the slow performance of many concurrent ad-hoc queries in Microsoft SQL Server.

see also:
224587 How to troubleshoot application performance with SQL Server
243586 Troubleshooting stored procedure recompilation