Froth flotation is the most widely applied technique for the beneficiation of low-grade and complex mineral resources, where separation efficiency is fundamentally governed by interfacial phenomena controlled by various factors, particularly flotation reagents, most importantly collectors. Despite substantial progress in collector development and adsorption studies, the characterization of collector behavior at the mineral-solution interface remains fragmented, with limited integration between physicochemical measurements, surface-sensitive analyses, and flotation performance. This lack of a unified, systematic approach hinders the transition from empirical reagent selection to predictive, design-oriented flotation chemistry. This review presents a comprehensive and structured analysis of interfacial physicochemical characterization methods used to investigate collector adsorption and their relevance to flotation systems. Key techniques (such as zeta potential analysis, contact angle measurement, adsorption analysis, and surface tension measurement) and their significant role in collector-related investigations have been comprehensively evaluated. Furthermore, outputs from emerging computational and simulation methods are incorporated to validate and complement experimental findings, enabling a direct link between macroscopic observations and molecular-scale mechanisms. The analysis demonstrates that, rather than relying on a single technique, which is insufficient to fully understand collector behavior, integrating complementary experimental and computational approaches yields the most reliable interpretation of collector-mineral interactions. The integration of these approaches provides a multiscale understanding of collector behavior, bridging bulk solution properties, interfacial interactions, and flotation performance. Based on these insights, the importance of a practical, flexible framework for collector characterization is established, emphasizing the selective, system-specific integration of techniques to optimize experimental design, reduce redundancy, and improve data interpretation. Overall, this work offers a unified, application-oriented perspective on collector characterization, advancing flotation research toward more predictive, efficient, and sustainable methodologies.