Then this data is put into excel and plotted 3-D to show the equipotential surfaces and to help students make the connection with gravity. Then they print out a 2-D black/white equipotential map and draw in their perpendicular E-field lines.
A variation of this activity is to use a container of water over a grid and the water is the conductor. I like this way because students actually see this as "real". With the conductive paper students don't see the lines drawn on the paper as being a 3-D object like a plate. In their minds this isn't real. It might be a good idea to use LED's to show the directionality of the e-fields in the water container.