Automated negotiation is widely applied in various domains. However, the development of such systems is acomplex knowledge and software engineering task. So, a methodology there will be helpful. Unfortunately, none ofexistingmethodologies can offer sufficient, detailed support for such system development. To remove this limitation,this paper develops a new methodology made up of (1) a generic framework (architectural pattern) for the maintask, and (2) a library of modular and reusable design pattern (templates) of subtasks. Thus, it is much easier tobuild a negotiating agent by assembling these standardized components rather than reinventing the wheel each time.Moreover, because these patterns are identified from a wide variety of existing negotiating agents (especially highimpact ones), they can also improve the quality of the final systems developed. In addition, our methodology revealswhat types of domain knowledge need to be input into the negotiating agents. This in turn provides a basis fordeveloping techniques to acquire the domain knowledge from human users. This is important because negotiationagents act faithfully on the behalf of their human users and thus the relevant domain knowledge must be acquiredfrom the human users. Finally, our methodology is validated with one high impact system.