Exotic mesons are mesons composed from something else than the standard quark-antiquark configuration of the naïve quark model. Glueballs, hybrid mesons, and multi-quark states are predicted only by calculations guided by Quantum Chromo-Dynamics. A large experimental effort for isolating such mesons has been undertaken in many laboratories around the world. The experimental results strongly rely on the interpretation of the data through Partial Wave Analysis (PWA). In this seminar, the development of PWA methods for pion beam diffractive dissociation, hadron central production reactions, and lepton-beam exclusive reactions will be discussed. Brief review of the results obtained by the VES (Protvino, Russia) and E852 (Brookhaven, USA) experiments will be given, including search for the spin-exotic JPC=1-+ state. The current situation with recent PWA analysis of the COMPASS (CERN) data will be reported.