Click and drag to rotate the camera.  
  Control-click and drag to zoom in/out.  
     
  C: Cycle through the three coordinate systems.  
  Control + Up/Down Arrow Keys: Move observation point in the first dimension of the current coordinate system.  
  Left/Right Arrow Keys: Move observation point in the second dimension of the current coordinate system.  
  Up/Down Arrow Keys: Move observation point in the third dimension of the current coordinate system.