Tom Brennan writes:
>capacatance is "one side of one of the plates".  I can understand the one side
>of one plate.  My question is how do you determine which plate is involved for
>this; is it simply determined by which pole of the cap is negative?

        Not really.  You have to have two plates separated by a
dielectric to have a capacitor.  There are even  antenna couplers
that work through glass.  They are nothing more than a pair of
metal plates that stick to each side of a window with the glass
being the dielectric.

        The thickness of the glass and accuracy of the placement
of the plates effects the capacitance and, if you have a metallic
film on the glass such as are on some windshields, forget it.

        On a variable capacitor with a stack of plates, each
plate's two sides add together except for the ones on the ends.

        Capacitors that pass RF have no positive and negative
poles.  They just appear to pass AC right through themselves.
The value of the capacitance and the frequency involved determine
the phase shift and the impedance of that particular capacitor.

        The only capacitors that do have a positive and negative
lead are electrolytic
and that is involved with D.C. signals.