IMac OS X performing slow/hangs

Question

My iMac system is performing slower than expected and often hangs. I often wait up to a minute for the next action to happen, while the little cursor sits and spins. What to do? Frustrating.
System specs that seem pertinent:
4G memory (2 slots taken; 2 slots free)
storage report says 176G free out of 499G
OS X, 10.8.2
Thanks, Apple community.

Answer 1

Most often this indicates you are running to many applications concurrently for the amount of physical RAM you have installed. It may also mean you have a crashed process:
Open Activity Monitor in the Utilities folder.  Select All Processes from the Processes dropdown menu.  Click twice on the CPU% column header to display in descending order.  If you find a process using a large amount of CPU time (>=70,) then select the process and click on the Quit icon in the toolbar.  Click on the Force Quit button to kill the process.  See if that helps.  Be sure to note the name of the runaway process so you can track down the cause of the problem.
While Activity Monitor is open click on the System Memory tab in the bottom portion of the AM window. Use COMMAND-SHIFT-4, use the crosshairs to select this portion of the AM window, then use the Camera icon of this message composition window to post the image here.