To select a node or a control point, click it.
To add to the selection, Shift-click a point.
To remove from the selection, Shift-click or Alt-click a point.
To marquee select one or several points, click in the empty space and drag around the area which you need to select. Marquee selection does not select handles (off-curve points), but this can be changed on the Editing page of the Preferences dialog box.