This document provides general guidance that is designed to help the U.S. Department of Homeland Security (DHS) Program Managers who may have limited expertise in simulation to better understand this technology. It is also intended to help the relevant professional community in developing better technical specifications for homeland security modeling and simulation (M&S) applications. Contractors outside of DHS typically develop homeland security M&S applications. Often the M&S applications that are developed today are difficult to extend for new purposes, integrate with other software systems, or used by persons other than the original developer/development team. Slight changes to a model or scenario may require major changes to a system and significant cost to the sponsor. Examples of topics (within the context of simulation) that are addressed in this report include: , Analysis of user needs and system requirements, Specification development: conceptual models, detailed designs, and interfaces, Modeling and simulation technologies appropriate to different problem domains, Use of proprietary commercial versus open source software, Project team and developer qualifications, Simulation engine, User interfaces, Inputs and output data types, Databases, data files, and translators, Documentation and training, Software risk management, Verification, validation, accreditation, and testing, Information security mechanisms, Distributed architectures and communications, Standards The technical guidance contained in this report is based on published literature, information available on the Internet, technical expertise, and personal experience.