Pandaren hunters automatically know how to tame Cloud Serpents. Hunters of other races must learn the skill from the tome How to School Your Serpent, which may purchased from San Redscale at The Arboretum in The Jade Forest. You require Exalted standing with The Order of the Cloud Serpent to read this tome, but the learned skill is account-wide. You can even purchase and read this tome on a non-hunter character.
Located in The Hall of the Serpent, Vale of Eternal Blossoms. Milau appears in the older, pre-Assaults phase of the zone. The Hall of the Serpent is located downstairs in Guo-Lai Halls, in the north of the zone.