When using the Van de Graaff you will need to use the large neon bulb.  Connect the ground of the Van de Graaff to one lead of the neon bulb and the other to either the rod with the point or the rod with the large ball on the end.  The rod with point will continuously discharge the Van de Graaff as indicated by the almost continuous glow of the neon bulb.  The rod with ball will draw sparks from the Van de Graaff with the neon bulb flashing with each spark.  Holding the ball farther away from the Van de Graaff will produce bigger sparks but be cautious as a very large spark may destroy the neon bulb.   

NOTE: Do not try this demonstration with the apparatus shown in picture 3 as the Van de Graaff potentials are enough to damage the amplifier. 

Charge the rod with the cat's fur.  Bring the pointed end of the tester, you should hear a low frequency sound that is made up of electrostatic discharges.  Charge the rod again and bring the rounded end of the tester to the rod and only one of two discharges should be heard.