G-protein-coupled receptors (GPCRs), the largest family of membrane proteins, represent ideal therapeutic targets for a number of disorders and diseases. Besides cell-based assays and high throughput screening (HTS), and thanks to the availability of milligram quantities of active purified receptors, protein-based approaches focusing on soluble GPCRs are growingly being used in this drug discovery effort. Along with the exploitation of GPCRs structures, innovative biochemical and biophysical approaches open up new routes for improving the knowledge of structure-activity relationships, for the identification of novel interacting partners and for the determination of receptor behaviour in different model environments. This review summarizes the state-of-the-art methodologies that robustly allow for the production and purification of soluble and active GPCRs, as well as the main outcomes that have been recently gained in GPCR biology using a panel of such protein-based approaches.