The vast majority of all information technology projects fail, principally because organizations cannot adapt their management and support processes to the rapid change of technology. These projects also fail because companies don't have the expertise to develop themselves into project-oriented organizations, and, therefore, are unable to put into place the project management techniques and tools required to effectively and efficiently manage IT projects.
There are many project management tools, but the most important four are:
The work breakdown structure (WBS)
The network analysis
The Gantt chart
The earned value analysis
Of these four, the most important is the WBS, because with a complete and accurate WBS, the project manager can develop every other tool she needs.