Hydrological signatures are index values derived from observed or modeled series of hydrological data such as rainfall, flow or soil moisture. They are designed to extract relevant information about rainfall– runoff processes, such as identifying dominant processes, and determining the strength, speed and spatiotemporal variability of the rainfall–runoff response. Hydrological signatures can be compared across catchments to understand spatial variation in runoff processes, and can be compared across time to evaluate hydrological change. Most studies use a selection of different signatures to capture different aspects of the catchment response, for example evaluating overall flow distribution as well as high and low flow extremes and flow timing. Such studies often choose their own set of signatures, or may borrow subsets of signatures used in multiple other works. There is little agreement towards a standardized set of hydrological signatures. In this opinion paper we discuss five guidelines to guide signature selection.