There is a thing called big data and small data and you gather these type of demographic information from research on competition, neighborhood demographics, lifestyle, family routines in and out of a home, sometimes jargon and slang can be key identifiers of niche groups, there is no single way of doing this but you do need to have a process in place that you can track your own work and see yourself getting to small demo each time. Look into Blue Ocean strategy practices, at Unthink, we use this to create campaigns for our clients even if we don't achieve blue ocean we get off the beaten path typically used by competitors and this has helped us achieve competitive advantage for our clients.