A communication plan is a written document that describes the objectives you want to accomplish and to whom and how your objectives will be communicated.
Communications can include written, verbal, and electronic interaction with your stakeholders.
When creating a communication plan a BA can always use the 5W1H method.
The communication plan should include the following:
Who = Stakeholders
What = Content, Detail, Techniques, Formality, and Language
When = Frequency
Where = Location
Why = Purpose and Importance
How = Tools used and Media