Here's an article that you might find helpful.

Taking Your Server's Pulse
http://technet.microsoft.com/en-us/magazine/2008.08.pulse.aspx?pr=blog

"Imagine you just arrived at the office on a Monday morning and you’re greeted by an eager user who is complaining that his server is running too slow. How do you even begin to help him? Performance
Monitor, a handy tool built into Windows®, can assist you in diagnosing the problem.
You can access Performance Monitor by typing perfmon at the command prompt or by selecting the Performance or Reliability and Performance Monitor (in Windows Vista® and Windows Server® 2008) from the Administrative Tools menu. To add performance counters and objects to be monitored, you simply click the plus sign and select from a host of possible choices.
So how do you measure the pulse of a server? There are more than 60 basic performance objects, and each object contains multiple counters. In this article, I will discuss the counters that reveal the vital signs of a server, and I will describe the typical sampling intervals that Microsoft® Service Support engineers use most often to troubleshoot performance-related issues.
Of course, a baseline provides a critical reference point when troubleshooting. Since the server load depends on the business requirements and also varies from time to time depending on the business cycle, it is important to establish a baseline determined by the normal workload over a specified period of time. That allows you to observe changes and identify trends."