I have worked on some memorable large-budget projects where I have used a series of spreadsheets or MS Project to plan and manage the whole thing. Rather surprisingly, I think all of these projects were a success but I wouldn't recommend the spreadsheet route for a complex project.
A decent project management tool will always help in the planning and managing of a complex, inter-related series of activities. That is because the more complex the project, the more likely it is that there will be problems, risks and dependencies so help in monitoring and anticipating these is far more likely to lead to a successful outcome.
Two commonly used methods in project planning are Gantt Charts and Critical Path Analysis Flow Diagrams. Gantt charts are a graphical illustration of a project schedule a bit like a horizontal bar chart that helps to plan, coordinate, and track project tasks. Critical Path Analysis is simply a time line showing all related and dependent tasks and activities in a project which helps tasks to be scheduled to prevent overlaps in dependent tasks.
When selecting a tool to help you manage a project, two of the most important factors to consider are how it handles Gantt Charts and Critical Path Analysis Flow Diagrams and, therefore, how the tool is going to help you with scheduling, resource management and dependencies. There are a number of very good proprietary software tools currently on the market but here are my top ten recommendations for open source tools:
But even the best tools are no substitute for a professional project management training course where you will learn tips and techniques about the underlying methods that will help you achieve a successful result.