We know surprisingly little about how, when and where quasars are triggered as galaxies evolve. In this seminar I will review quasar triggering mechanisms, and present the results from an optical and far-infrared study of a large sample luminous radio-loud AGN that cast direct light on the quasar triggering issue, demonstrating that galaxy mergers are the most likely triggering mechanism. Along the way, I will emphasise the importance of taking full account of the AGN-related continuum components when determining the host galaxy properties. Also, I will discuss the reasons for the apparent dearth of star formation activity in the most luminous AGN.