A discovery method by Christian Idiodi
Christian Idiodi's Reference Customer Method for Product-Market Fit
Christian Idiodi is a partner at Silicon Valley Product Group. His answer to "how do I know what to build" is not a survey or a backlog score: pick a specific, countable set of customers, six to eight for B2B and fifteen to twenty-five for B2C, and build the product with them until they will personally recommend it. The word reference is doing two jobs. They are your reference for what to build, and they become the reference that sells the next customer.