I have to suggest that you follow the guidelines in the document Greg mentions. Anything else, you're sort of on your own.
If you get the 0-100-0 effect with a mono cable, this means that you are using a volume pedal rather than a pure expression pedal. You can fix this by cutting off the wire going from the ring connection on the jack to the control. Or, you could replace the mono jack plug with a stereo one, and leave the ring unconnected.