Now, enter the realm of systems monitoring. On every Unix system, there are a few monitoring tools available and they grow in number as days go by. The most commonly used commands to monitor a Unix systems performance follows (classics):
uptime - Tell how long the system has been running. (More onto this really.)
procinfo - display system status gathered from /proc
who - show who is logged on (Also more onto this.)
top - display top CPU processes (Resource hungry though...)
Those above commands are very useful in determining the actual System LA (Load Average), this metrics can also be used in performance analysis and capacity planning.
The following link below, you will learn System Load Average in the more in depth manner. I would like to thank Dr. Neil Gunther for his wonderful insight. And also everybody that contributes to the Unix and Unix-like Operating Systems. And I would like to encourage every Systems Administrators to always read the man pages.