First, you use drag-select to select a group of nodes.
Then, you use CtrlClick to unselect individual nodes.
Finally, you use ShiftClick to add nodes to your set and then click mouse button 2 to indicate you have finished selecting.
You may find it useful to adjust the view orientation to make particular items in the viewport more accessible. You can adjust the view orientation at any point during the selection process. For information on the view manipulation tools, see Manipulating the view and controlling perspective.”