The deployment of a geographic location service for Internet hosts enables a whole new class of location-aware applications. We focus on a technique that infers host locations using delay measurements to geographically distributed landmarks, which are hosts with a known geographic location. The problem we deal with is where to place such landmarks and the probe machines that perform the delay measurements. We propose a demographic placement approach to improve the representativeness of each landmark with respect to the hosts to be located. Results show that a relatively small number of landmarks is sufficient to cover the most part of hosts to be located. For a fixed number of landmarks, the demographic approach reduces the distances from most hosts to the nearest landmark. Considering the probe machines, we show that they have to be sparsely placed to avoid gathering redundant data.