Some criteria and design rules useful for the elaboration of sensors based on force-balanced capacitors are shown. To achieve this goal we have interrelated the mechanical and geometrical properties of the system with the final working features, such as sensitivity, bandwidth, full-scale range and maximum controlling voltage. To derive these relations we have also applied stability criteria. Moreover, as the optimization of the electronic feedback control of micromechanical structures can be improved by an accurate knowledge of mechanical parameters such as resonance frequency and damping ratio, we have also included a finite-element method (FEM) to determine the pressure distribution and damping ratio of any mechanical configuration immersed in a viscous fluid.