We give a new proof of the classification of normal singular
surface germs admitting non-invertible holomorphic self-maps
and due to J. Wahl. We then draw an analogy between the
birational classification of singular holomorphic foliations on
surfaces, and the dynamics of holomorphic maps. Following this
analogy, we introduce the notion of minimal holomorphic model
for holomorphic maps. We give sufficient conditions which ensure
the uniqueness of such a model.