Go to the resource view, click on the icon with three little bars of increasing height (underneath the Connection icon in the image below). Now anywhere you see a pink/red blob underneath a task in the right hand side of the window, you've got a resource being overcommitted. When the blue bar doesn't come all the way up to the middle line, you've got a resource being underutilized. If you don't select any of the resources on the left, the view on the right shows all of them, otherwise it only shows the selected resources.
