Design for everyone is design for no one.
At the beginning of each new project, product design firm Design that Matters creates a point of view statement to focus the project on the need, users, and contexts that will be included and excluded from the final design. While written for project teams that are designing things, the same process can be employed by people designing communications. This exercise makes the creative brief that much more useful and relevant.
Article: Design Experience That Matters: How Focus Leads to Bigger Impact