Keep the Project Plan as Simple as Possible
What is the project going to do? (SCOPE)
What is the project going to cost? (RESOURCES)
When is the project going to be finished? (SCHEDULE)
If the plan addresses those questions, then it is usable. If not, there needs to be more work on the plan. Each of the questions can be expanded, (perhaps greatly), of course. Most plans have entire sections that address the three questions with various degrees of coverage.
The primary constraint to consider is the scope. What will get done? This question implies that an earlier statement, or purpose, was identified first. Call this the project overview or preliminary scope statement or a similar term. It is an overall guide for the team. Consider this example:
...this nation should commit itself to achieving the goal, before this decade is out, of landing a man on the Moon and returning him safely to the Earth.
President J.F. Kennedy, 1961.
This scope statement establishes the guiding principle for the project. It was established with authority, the then current president of the United States. All future project planning could refer to the initial statement for guidance.
What was the space program supposed to do? Put a man on the moon and return him safely to the Earth. While there were tragic accidents prior to Apollo 11, the first man to land on the moon was returned successfully.
When was the space program supposed to do it? Before the end of 1969. Since the mission did accomplish the goal of landing a person on the moon on July 20, 1969 and returning that person on July 24, 1969, the schedule was met. In fact, there were over five month's of spare time in the decade.
What was the cost of the space program? This basic question of the project was not addressed in the preliminary scope statement. This is often the case as there is so much unknown information in the beginning. As budgets were estimated and funded, the cost was better understood. In the end, the authority of the project won out and the required money was allocated.
The process used to enhance the triple constraints during the planning process is called progressive elaboration. Each of the constraints is analyzed to better specify the issue in finer detail. "What are we going to do?" becomes a scope definition document with several layers of detail. A work breakdown structure may be formed to define the scope. In the first version, our example may have these subordinate steps:
Project: Land a man on the moon and return him safely to the Earth
Step 1: Transport a manned vehicle to the Moon
Step 2: Safely land the vehicle on the surface of the Moon
Step 3: Safely return the vehicle to the Earth
This scope is easier to discuss now but there should be finer scope definition:
Step 1a: Build a vehicle that will sustain a man in the vacuum of space
Step 1b: Build a propulsion system that can lift a vehicle off the Earth and transport it to the Moon
Step 1c: Build a vehicle that can land on the surface of the Moon
Step 1d: Build a vehicle that can return from the Moon to the Earth
Notice that these sub-steps call for various vehicles to do certain things. In the real Apollo program, there were only two vehicles used for each mission. That is a scope implementation detail. It is only after analysis of possibilities that such options as examined and chosen or not. The point is to keep the steps simple so that they can be accomplished. With the Apollo space program, simplicity was not really possible since so much of the needed technology was not available and had to be invented for the project. This is a problem that can have drastic consequences on the risk of the project.
When working on a project plan with the goal of keeping the work as simple as possible, try to always reduce the scope. Notice that President Kennedy did not say "send a group of men to the Moon several times". His scope specified one man, one time. NASA elected to send three men on the mission, land two and return all three to the Earth. The final scope was larger than the President envisioned but was likely necessary due to the overwhelming amount of work that a single man would have to perform. The increased scope added to cost and risk. Three men need much more space and resources than one.
In the end, the NASA space program was successful when Apollo 11 reached the Moon and returned safely. While the project was extremely complicated, and involved huge amounts of complex planning, the overall purpose was simple to understand. This is a mark of a successful project. Of course, the space program was completed early when Apollo 11 returned to Earth. Pure adherance to project methodology would declare that an early project is unsuccessful. In the Apollo 11 case, however, they may have planned to have a few months left over in the decade in case bad weather delayed the liftoff. The project documented such lessons learned so that they could be a reference to future project managers.
While your projects may not be as complex, or expensive, as the space program, they will be time consuming and important to you. Try to keep them simple. Get simple declarations of scope. Keep the scope manageable. If something isn't absolutely needed, keep it out of the project. A good way to accomplish this is to defer items to a subsequent phase if they can't be eliminated. Get good time estimates for each scope task. Schedule implies cost so get reliable costs for staff hours and other needed resources. Be aware of risk.
It is often because of risk that projects are made more complex. NASA was aware that the harsh environment of space was extremely damaging to the newly invented computer chips. They invented specifications for chips that would survive in space. This added great cost to the program and complexity to the project, of course. Your projects may avoid this kind of risk planning but they will run into their own obstacles that cause complexity to rapidly creep into your plan.