Abstract
Extra neutral gauge bosons suggested by models beyond the standard model can indirectly show up in e+e- collisions through off-resonance deviations of various physical observables from the corresponding standard model values. We considered leptonic observables and studied the dependence of the deviations on the polarizations of the positron and electron beams. We showed that, for a given model, the magnitude of the deviation of a given observable can attain its maximum value if the polarizations of the positron and electron beams are properly chosen. We determined, for a given model, a single set of beam polarization so that if this set is employed in measuring all considered observables, it produces the highest extra gauge boson discovery limits.