Methods employing the diffraction and scattering of X-rays, electromagnetic radiation with photon energies ranging from about 100 eV to 100 keV, are arguably the most important characterization tools available to materials researchers. X-ray scattering experiments provide versatile, quantitative, accurate, and precise characterization of the structure and properties of materials. In the context of the epitaxial growth of metal oxides, X-ray diffraction (XRD) is almost always the first characterization technique employed after material synthesis: a relatively straightforwardly acquired \(\theta - 2\theta\) scan, for example, immediately provides valuable feedback about whether the growth process was successful or not. The last few decades have seen tremendous progress in the use of XRD to study thin-film oxides. Instrumentation allowing the rapid acquisition of X-ray reciprocal space maps—once only available at stations on the beamlines of synchrotron-radiation light sources—is now available off-the-shelf and installed at many universities and research institutes. Our goal here was to construct a detailed and practical guide to the methods that researchers employ daily. The chapters of this book distill what the authors have learned—and incorporated into multiple research papers—into guides for students and other researchers who are beginning to grasp how to carry out a particular XRD technique. The techniques and analysis methods described here allow a broad number of physical properties of epitaxial thin films to be probed, ultimately bringing deeper understanding into these fascinating and technologically relevant materials.