The first article is Exchange 2010 counters information from the Technet.
The principle described in the second and the third article can be applied or declined to any versions of Exchange.
1> The general counters values and thresholds for all Exchange 2010 servers, and narrowed by role:
2> From Nicole Allen from the Exchange Team : how to investigate Exchange performance issues:
3> An nice and concise article from one of our Exchange MVP, Ratish Nair that nicely summarizes the above articles :