The phrase develop project management plan refers to the act of itemizing the specific list of all items that are going to be deemed necessary (or perhaps even essential) to the successful definition, integration, and preparation of all subsidiary plans into the final and ultimate project management plan. This is typically best done at a very early stage in the project planning process as a number of subsequent planning activities are dependent on the knowledge of the specific items that are deemed to be essential as indicated above. The development of the project management plan may be something that is drafted by the project team leader, it may be arrived at via consensus discussion among all project team members, or it may be something that is provided to the project team for review by an executive management team, who typically is more closely attuned to the financial specifications and revivifications of the big picture. However, in these cases it is essential that the project team be given adequate opportunity to review and comment on this plan.
This term is defined in the 3rd and the 4th edition of the PMBOK.