Wireless indoor positioning has been a popular research topic for years because it provides the basis for a broad domain of location-based applications. Especially the usage of WLAN (Wireless Local Area Network) technology is widespread to build an indoor positioning system due to the reuse of existing and almost ubiquitous WLAN infrastructure worldwide lowering the costs. However, these WLAN systems were not originally designed for positioning services, thus the provided accuracy might be low. The accuracy can be increased by the careful placement of WLAN access points to cover the given area appropriately. In this paper, we propose a method based on simulated annealing to find the optimal number and placement of WLAN access points for indoor positioning and show its investigation using simulations.