This 11 page PDF will help ballet teachers and students with:
breaking down all the elements required for perfecting pirouettes
understanding the different types of ballet pirouettes
how to get the best posture and core
the importance of centreline and finding your axis
spotting and eye focus
weight placement in preparations
momentum
leg and glute exercises to help balance and supporting leg
turnout and core exercises for technique
upper body and arm exercises to strength and placement
technique breakdown and advice for 
Pirouette en dehors
Pirouette en dedans
Chainés
Posé pirouette en dedans
Posé pirouette en dehors