The are taught through consistent training that emphasizes:

Striking the ball of the foot against the floor from a flexed neck-of-the-foot ( cou-de-pied ) position, simulating the initial strike phase of a jump.

Basic Principles of Classical Ballet: Russian Ballet Technique

One heel placed against the arch of the other foot.

One foot placed directly in front of the other, with the heel of the front foot touching the big toe joint of the back foot. 4. Placement and Port de Bras

If you locate a PDF or physical copy of the book, you can expect the content to be structured as follows:

A dancer must maintain a strong, vertical alignment (plumb line) to achieve stability and balance.

Turn-out is the foundation of all five classical positions of the feet. 2. The Five Positions of the Feet