Energetics and conductance in jellium-modeled nanowires are investigated using the local-density-functional-based shell correction method. In analogy with studies of other finite-size fermion systems, e.g., simple metal clusters or He-3 clusters, we find that the energetics of the wire as a function of its radius (transverse reduced dimension) leads to formation of self-selecting magic wire configurations (MWCs, i.e., discrete sequence of wire radii with enhanced stability), originating from quantization of the electronic spectrum, namely formation of subbands that are the analogs of electronic shells in clusters. These variations in the energy result in oscillations in the farce required to affect a transition from one MWC of the nanowire to another and are correlated directly with stepwise variations of the quantized conductance of the nanowire in units of 2e(2)/h.