What is the best way to generate Metta

Buddha said that we should train ourselves in *metta* in the following way: "Thus you should train yourselves: 'Our awareness-release through good-will will be cultivated, developed, pursued, handed the reins and taken as a basis, given a grounding, steadied, consolidated, & well-undertaken. That's how you should train yourselves." -- Satti Sutta How do monks cultivate *metta*? Is it by some kind of remembrance, recitation or something else?