UX designer and journ­al­ist, 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?”