Recently, we have shown for a number of different systems that adsorbates with comparable electronic energy levels interact with the same surfaces in a similar way. The degeneracy of the energy levels now fully describes how different energies correlate and each line shift according to the surface structure (its reactivity). This means that we can determine the energetics of a reaction from much fewer calculations. Such models of reactivity trends that single out the important parameters describing the catalytic activity or selectivity are the essential prerequisites for the tailoring of surfaces with specified catalytic properties. In principle, there are many parameters that enter into the kinetics of a given reaction: the energy of all intermediates and of the transition states separating them is needed to specify the energetics.