Excerpts from book:

The Importance of Project Planning
GIS projects are expensive in terms of both time and money. Municipal GIS and facilities management projects developed by utilities may take a decade or more to bring on-line at a cost of tens or hundreds of millions of dollars. Careful planning at the outset, as well as during the project, can help to avoid costly mistakes. It also provides assurance that a GIS will accomplish it goals on schedule and within budget.

There is a temptation, when a new technology like GIS becomes available, to improvise a solution to its use, that is to get started without considering where the project will lead. The greatest danger is that decisions made in haste or on the spur of the moment will have to be reversed later or will prove too costly to implement, meaning a GIS project may have to be abandoned. To avoid disappointing experiences like these, GIS professionals have developed a well-defined planning methodology often referred to as project lifecycle. Lifecycle planning involves setting goals, defining targets, establishing schedules, and estimating budgets for an entire GIS project.