Despite the existence of several highly effective and well-characterized passivating materials for crystalline silicon surfaces, the topic of surface passivation and the investigation of new passivating materials remain of considerable interest for silicon photovoltaics research. However, the question of whether and under what circumstances a particular material will provide effective surface passivation remains difficult to answer. In this work, we provide an overview of recent insights relating to this question, drawing from our own work on novel passivation materials including MoOx, Nb2O5, TiOx, ZnO, and POx, and illustrated with experimental results. Factors that strongly influence the passivation performance include the use of pre-grown interfacial oxides, the film thickness, the annealing conditions, and the presence of capping layers. The impact of these factors on the surface passivation can vary widely from material to material. Therefore, all of these factors should be taken into account when investigating potential new surface passivation materials.