There seems to be a paucity in the research into the collection of data for use in simulation. This is rather unfortunate since data quality and availability are two of the most challenging issues in many simulation projects. In this paper, we are interested to know how practitioners identify and collect data for simulation projects. An action research was conducted at the ORH Ltd, a management consultancy company to evaluate their data collection guidelines using a real project conducted for a UK Ambulance Service to recommend new staffing levels to deal with increasing calls and to incorporate the installation of a new operating system. We discuss the issues surrounding the identification and collection of data which can be divided into data-related and process-related issues. We propose an improvement to the data identification and collection methodology to reduce the number of cycles in the data collection process.