In this work we present the model capable of prediction whether the vapor-liquid-solid growth would preferably result in the formation of in-plane (horizontal) or out-of-plane (vertical or inclined) nanowires. Within the model, we analyze the particular case of gold-catalyzed germanium nanowire growth on Ge(111), Ge(110) and Si(100) substrates. We focus on two aspects of the growth process: detachment of the catalyst from the substrate and stabilization of horizontal growth by nucleation at the nanowire-substrate-liquid line.