Asanas are the visual component of yoga practice. They are to be practiced in conjunction with the following four unseen/perceived components:

• Ujjayi Breath  (Victorious breath)
  The continous inhalation and exhalation through the nose involving the use of the diaphragm and abdominal muscles.
  
• Bandhas (Locks)
• Moola Bandha (Root Lock)
  Is situated at the base of the spine, and engaged by contracting your butt muscles.
  
• Uddiyana Bandha (Abdominal Lock)
  Is situated below the navel, and engaged in between inhalation and exhalation by lifting of the diaphragm.
  
• Jalandhara Bandha (Chin Lock)
  Is situated at the chin, and engaged by pressing the chin against the adams apple.
  
• Vinyasa (Flow)
  The deliberate movement through which we flow from one posture to the next to keep the continuity.
  
• Drishti (Gaze)
  The direction in which you turn your eye's gaze in a posture.