This chapter is dedicated to the quality of the powder diffraction pattern, which is of utmost importance, especially when structure solution and refinement are the goal. This is reflected in the well-known saying: Do not waste your time on poor data. The two most important factors affecting quality—sample preparation and data acquisition—are considered in detail. While the former is largely in the hands of the user, the latter, to a great extent, depends on the configuration of the available instrument; even so, user input is still required to get the most from the instrument. Taken together, these considerations make this chapter essential reading.