A collection of state-of-the-art methods for interrogating ligand-receptor and receptor-effector interactions. Methods emphasize the regulation of G protein-coupled receptors and focus on receptor characterization, methods for investigating how receptors couple to G proteins, and approaches to studying how receptor expression and function is regulated. The easily reproducible protocols include chimeric receptor construction, antibody generation, transient and stable transfection methods, hybridization, as well as immunocytochemistry, functional assays of G protein function, and antisense methods for defining receptor-effector coupling pathways.