I gave a talk entitled “Predicting Project Completion” at the Central Mass chapter of the PMI last night. I had some suggestions about techniques to generate and discuss schedule estimates. Then, to practice a little, I asked the audience to become participants and practice a simulation. The simulation is to first estimate how long it will take to sort two decks of cards (I only allow three minutes for this part), and then to do the sorting, comparing the estimated time with the actual time.
As I debriefed the simulation, some of the people said, “Three minutes is not long enough to plan this project. Some people disagreed, “Three minutes is plenty of time to plan the project–because we can't fully plan, so we can plan enough in three minutes to get started.”
I don't know how much time is enough time to plan your projects. It depends on where your risks are: in the people not knowing the subject domain; in the pre-determined costs; in the whether you have enough people assigned when you need them; whether the feature set is known or will evolve; whether anyone knows how good the project needs to be. You probably have more risks on your projects.
But I am sure that for a projects of more than one person and more than one week in duration, three minutes is not enough planning. Our projects last night had actual durations of about 2.5 minutes to 7 minutes. Taking more than three minutes to plan would have been nuts–we could have spent more time planning than working. But I regularly see 6-12 month projects where the PM and technical leads spent less than three minutes planning (by their own admission).
I recommend starting every project with a project charter, and taking an hour or maybe two with the technical leads (or on a small project, with each person) participating in generating the charter. You may not know precisely where you're headed, but you'll already have generated some shared goals, which will help you make the decisions as you proceed. Once you've spent that hour or two, you can decide if you need more planning at the beginning of the project, or if you can continue to plan as the technical staff proceed, or if you iterate the plan as you proceed (or both).
There is no One Right Way to start a project, but a project charter can help. Taking just enough time to charter the project may help you understand where your project's risks are, and how to deal with them. And that may be about enough planning.