Scenario

At the beginning of a project, it is not always possible to define in great detail all of the requirements, work elements, and deliverables that will be involvedespecially when a project is scheduled to last for a long time or involves several phases. In such cases, details can be progressively elaborated as the project evolves. As these details are established and addressed, however, the scope of the project may seem greater than originally anticipated, and revisions may be necessary.

Question

How should a project manager or team go about managing changes to the Project Scope Document, and what are the points and pitfalls that should be kept in mind?