Visit the ESRI Project Center for resources to help you consider the strategic purpose of GIS for your organization.
When planning for a successful GIS, you must think first about what you want from it. Everything else you do comes from that vision to ensure that the GIS will ultimately work towards serving some useful and important purpose.
Start by considering the strategic purpose of the organization within which the system will be developed. What are its goals, objectives, and mandates?
This stage of the planning ensures that the process and the final system fit within organizational context and truly support the strategic objectives of the organization. This stage also allows you to assess how information created by the GIS will impact the business strategy of the organization.