It is key to break down your work into packages that make sense to the team.

The smaller you break it down, mis-communication and risk can be managed easier.

It is a balance though - as to how much time and effort is spent on breaking it down during the planning stage. Thus be aware and align with the risk tolerance or risk thresholds that exist within the project.

Decomposition is the breakdown of project deliverables into smaller, more manageable components until the work and deliverables are defined to the work package level. The work package level is the lowest level in the WBS. Generally, the hierarchy of the breakdown levels include:
1 - Phases
2 - Deliverables
3 - Sub Deliverables
4 - Work Packages

Note: the next beakdown level is to focus on a verb-noun format and is now at a much greater level of detail but Project Management Institute ( considers this a separate part of the work plan, essentially an Activity List is a sub-set of a Work Package (however some people consider this to be an extension of the WBS which is common business practice).
5 - Activites
6 - Tasks

Decomposition of the upper level WBS components requires subdividing the work for each of the deliverables or subprojects into its fundamental components, where the WBS components represent verifiable products, services, or results.

The most bottom level (work package) is the point at which the level of cost/effort and amount of time for the work can be estimated with a strong level of confidence. The level of detail will vary with the size and  complexity of the project, knowledge/experience of the team and timeliness of project deadlines. The adequate level of detail is often when the work can be easily delegated to an owner who can complete the task with little risk of misinterpreting of what work needs to be completed.

Some deliverables may not have enough details, information available, or clear understanding of the scope so detailed breakdown can be delayed until later in the project. This technique is sometimes referred to as rolling wave planning.

As the work is decomposed to lower levels of detail, the ability to plan, manage, and control the work is enhanced. However, excessive decomposition can lead to non-productive management effort, inefficient use of resources, and decreased efficiency in performing the work. The project team needs to seek a balance between too little and too much in the level of WBS planning detail.

A good way to support this concept is to always use Nouns in the WBS. There should be no action words (verbs). A verb generally indicates you have broken down the work too far. The level that utilizes verbs will be discussed in the Activity List section.

It is critical to have a strong facilitator conduct the WBS sessions. Generally the Project Manager will act in this role. The first priority is to ensure the correct stakeholders are involved at the most efficient and effective levels that are being broken down. For example invite higher up management to breakdown the highest levels of the WBS and lower level managers, more hands on to breakdown the lower level more detailed work. Ensure all stakeholders understand the sum of all the work before starting and at the end of each session.
It is generally more effective to focus on smaller areas of the WBS at a time (not the entire WBS), unless it is the first session and you have a diverse group of stakeholders that can address all areas of the project. If you are breaking down the work and are not successful at getting to the detailed levels, reassess the invitation list and ensure the correct roles are involved in the next session.

To have a team identify and agree upon all the work that is required to complete the project requires patience, cooperation and very strong analytical thought processes. Structuring and organizing the project work into a WBS that can meet requirements of the project management team and the key stakeholders requires great effort and commitment. Any opportunity to leverage work that has been done before is highly recommended.

Although each project is unique, a WBS from a previous project can often be used as a template for a new project, since some projects will have certain areas of work that are similar. Many organizations have standard WBS templates for the specific area of work (functional departments).

The resulting structure can take a number of forms, such as:
• Using the major deliverables and subprojects as the first level of decomposition;
• Using subprojects where the subprojects may be developed by organizations outside the project team. For example, in some application areas, the project WBS can be defined and developed in multiple parts, such as a project summary WBS with multiple subprojects within the WBS that can be contracted out. The seller then develops the supporting contract work breakdown structure as part of the contracted work;
• Using the phases of the project life cycle as the first level of decomposition, with the project deliverables inserted at the second level;
• Using different approaches within each branch of the WBS, example feasibility, analysis, design, actual product, service or end result, testing, pilot, training, support/warranty, etc.

An easy way to further understand the WBS concept is to view the numerous types that exist and can be leveraged as "boiler templates" for your work.  One can easily conduct a search on the web for WBS Templates or check out the link below:

WBS Sample Templates