Luminescent semiconductors are the key material in a host of optoelectronic devices including solar cells, light emitting diodes and x-ray scintillators, and have been discovered at an increasing rate over the last decades. A luminescent semiconductor’s photophysics must be understood and its loss processes minimized to optimize any device. Several accessible spectroscopic techniques exist which, together, can give all relevant photophysical information, namely UV-Vis spectroscopy, photoluminescence quantum efficiency and time resolved photoluminescence. However, these measurements are often poorly used, incorrectly fitted or important information is missed. Here we present best practices in applying these techniques to characterize luminescent semiconductors with unknown photophysical properties. We highlight which information can be obtained from each measurement, when it is appropriate to apply different mathematical models and give examples from a range of semiconductors. This work will help standardize and streamline the characterization of luminescent semiconductors, in turn enabling more efficient devices.