We did an open card sorting exercise, meaning we started by identifying the issues our agents hear most frequently and then proceeded to collectively work them into categories. Categorization was done based on how inter-related or independent these issues were. We ended up with 17 top level categories, which were fairly straight forward to prioritize simply by looking at the contact logs.
A customer care stakeholder worked with an internal copy writer to define the content under each card. Together they used an existing CMS to make the updates to the live FAQs page.