UX designer and consultant, Hunter Whitney, describes a good mindset as you start digging into data, with the end target of visualization. "Why might you want to collect data about something and are you sure you know what you really need? ... How are the data stored? ... How are they summarized (statistically) and modified? ... How are the charts displayed, formatted, and presented in the context of the full interface?"
[UX Magazine | Thanks, Elise]