How do I select and manipulate a rig? Downloaded this IK rigged model: http://www.blendswap.com/blends/view/72307

Opened it in Blender, but I'm not able to figure out how to interact with the rig. When I try to select one rig/joint, Blender selects the whole rig/all the joints. How can I select one, and only one rig/joint(for instance, the foot)?

I've used Blender for other stuff for a couple of months. I've also animated in other software, so I'm not new to the theory. I just don't understand Blenders interface for using rigs.
You must be in Pose Mode.

Press CtrlTab with the rig selected, or select pose mode in 3D view > Header: