It depends on the stage of the process and what you intend to accomplish. In general, prepare material beforehand including, customer feedback, a competitive audit, company values, and existing brand artifacts. Work with leaders from different parts of the company, especially marketing, product, design, as well as the CEO to define the attributes you think the brand should convey.
Show what customers say
Present the common reoccurring positive attributes customers use to define their experience. Your brand should magnify these virtues. Ideally, you have a list of feedback to draw from. If not, set up some customer calls or surveys to solicit feedback.
Examine what the competition does
How do other related companies or products position themselves? How is your offering different? Preparing a competitive audit that showcases visual style and voice and tone will help guide the discussion.
Distill values and feelings
Brand is the communication of values and associated feelings. What are your internal company values? What is your mission and vision for the future? These artifacts will help form a foundation for discussing brand.
Present existing brand artifacts
Present a brand audit. How does your company or product currently present itself? What feels right and wrong?
Ask company leaders what they think the brand should convey
Ask each participant to describe the feelings, associations, and values they think the company or product conveys. Write each attribute or value proposition down and categorize it. If greater formality or structure is needed, employ a card sorting exercise where participants choose from a set of fixed attributes or allow them to write it down and categorize common patterns.