The desire to flexibly customize software, manage it efficiently, and empower it with intelligence has driven research and development-related efforts toward intelligent agents. The benefits in terms of rapid delivery, reduced costs, and enhanced productivity can be realized in the areas of systems and software engineering with the proliferation of this technology. Intelligent agents represent an alternate approach to distributed software engineering. Agent-oriented conceptualization provides a new paradigm for the design and development of these agent-based systems. This chapter extends and formalizes this agent oriented modeling approach to the conceptualization process. It defines agent models and proposes a high-level methodology for agent-oriented analysis and design. It also looks at the heart of agent-oriented programming and outlines its advantages over traditional approaches to distributed computing and interoperability. The chapter includes analogies with the object-oriented methodologies and other existing agent-oriented methodologies wherever applicable. It reviews the Foundation of Intelligent Physical Agents-compliant infrastructure for building agent-based systems and suggests a multi-agent systems framework that merges this infrastructure with the emerging J2EE technologies. The chapter concludes with a case study and an insight to future challenges.