There are two fundamental approaches that can be used to identify project activities and tasks. The first is the top-down approach; the second is the bottom-up approach.
The top-down approach begins at the goal level and successively partitions work down to lower levels of definition until the participants are satisfied that the work has been sufficiently defined and they have reached the task level as determined by the completion criteria.
In my consulting practice, I have used two variations of the top-down approach: the team approach and the subteam approach.
The team approach, while it requires more time to complete than the subteam approach, is the better of the two. In this approach the entire team works on all parts of the WBS. For each Level 1 activity, appoint the most knowledgeable member of the planning team to facilitate the further decomposition of that part of the WBS. Continue with similar appointments until the WBS is complete. This approach allows all members of the planning team to pay particular attention to the WBS as it is developed, noting discrepancies and commenting on them in real time.
When time is at a premium, the planning facilitator will prefer the subteam approach. The first step is to divide the planning team into as many subteams as there are activities at Level 1 of the WBS. Then follow these steps: