Scope planning is "creating a project scope management plan that documents how the project scope will be defined, verified, controlled, and how the WBS will be created and defined". You begin doing the scope planning process by using the inputs that will give guidance to the project manager. The inputs to scope planning have been discussed elsewhere. They are enterprise environmental factors, organizational process assets, a project charter, preliminary Scope Statement, and the project management plan. All five of these are needed to begin doing scope planning.
The organizational process assets describe processes that are in place in the organization that will be useful in doing the scope planning. Any organizational policies and procedures that are already in place and pertain to scope planning and management are considered assets, as would be historical information about previous projects, according to the 3rd edition of the Section. Historical information can be in the form of lessons learned, although historical information is available in many other formats, such as reports and requirement documentation from previous projects.
A word on the preliminary Scope Statement is necessary. The preliminary nature of the Scope Statement listed in this scope management process indicates that the preliminary Scope Statement is not the final Scope Statement to be used to manage the project. Be careful to understand that a Scope Statement is not final until it is locked under version control, and only then will it be the baseline for your project. This is an input in the scope planning, not the final Scope Statement.
The tools and techniques for scope planning include expert judgment and the various templates, forms, and standards that are useful in constructing a Scope Statement. The Scope Statement is your baseline and one of the most important documents you have on a project. The Scope Statement that is given to the project manager at the beginning of the project is the baseline of scope for the project. It should be put under change control, and any changes to the Scope Statement should require a new version number. Failure to control the Scope Statement carefully and rigorously will result in major problems as the project is executed.
The various templates, forms, and standards that are inputs into scope planning can come from a variety of places in a variety of forms. You should check with your organization to see which types they have for use.