In public safety and homeland security, it is important to understand technology users' primary goals, the characteristics of the users, and the context in which they are operating. New and emerging technologies present opportunities and challenges for public safety standards. As part of the Public Safety Communications Research (PSCR) effort, the National Institute of Standards and Technology (NIST) usability team is currently researching the usability of communications technology for first responders. This is a large, multiphase research project, with the ultimate goal of developing a standardized usability testing and evaluation methodology for public safety communications technology. In this document, we discuss our application of a user-centered research methodology to investigate first responders' technology and communication needs. We present the details of the initial phase of the project, including our methodological approach and results from working with subject matter experts (SMEs) in fire, emergency medical services (EMS), and law enforcement fields. We conducted in-depth interviews with 133 SMEs to understand their perceptions and attitudes towards communications technologies and their information and data needs during incident response. We found that information and data needs can vary based on user role, tasks, and the context and scope of an incident. User needs and requirements have been organized into five categories of technology opportunities. Further analysis identified six user-centered design guidelines for technology development. Data resulting from this user-centered research can help inform usability testing methodology and standards for homeland security and public safety.