1. A method of determining a measurement subset of metrology point locations, the measurement subset comprising a subset of potential metrology point locations on a substrate, and the method comprising: identifying a plurality of candidate metrology point locations from the potential metrology point locations; evaluating for each of the candidate metrology point locations, a change in the level of informativity imparted by the measurement subset of metrology point locations which is attributable to the inclusion of that candidate metrology point location into the measurement subset of metrology point locations; and selecting for inclusion into the measurement subset of metrology point locations, those candidate metrology point locations which have the greatest increase in the level of informativity attributed thereto.