To edit a polygonal object, simply click on one or more vertex points and drag any direction. The surface of the object redraws to show the changes.
You can pull more than one vertex point at a time. For example, to stretch a sphere into an ovoid, select multiple points by shift-clicking or using a selection marquee. Then, drag them in unison.
NOTE: You can only select vertex points that are visible, so you must be in Wireframe, Outline, or PointCloud display modes in order to select backfacing vertex points. In addition, the Backface Culling option on the Windows tab of the Preferences dialog must also be disabled to select backfacing points.
To move points perpendicular to the active grid, use the Command + Shift keys (Macintosh) or the Ctrl + Shift keys (Windows). A temporary grid line appears to assist you in the proper placement of the selected vertex points.