The ancient sage Patanjali initially systematized and documented the practices of Ashtanga Yoga. He described this process as having eight limbs (Ashta = eight, anga = limb). As with every system of well-being, each individual expresses the principles uniquely. The eight limbs are:
Restraints (Yama) : Never be violent, always be truthful, avoid misappropriation of material or non-material (such as praise) things, exercise sexual responsibility, practice non-possesiveness.
Observances (Niyama): Maintain cleanliness of body and mind, control desire, study Wisdom teachings, surrender to God--to What Is.
Posture (Asana): This is what many people think of as Yoga. It is Yoga, but Yoga is not just asana. "Asanas help to balance the physical body by regulating glandular secretions, toning muscles and nerves, massaging internal organs, and improving circulation and digestion" (Baba Hari Dass). The purpose of asana is to prepare the body to sit comfortably in meditation for long periods of time.
Breath Control (Pranayama): Prana is subtle vital energy. Ayama is expansion of and control over. "Pranayama is a method of breathing through which life-supporting energy is expanded" (Baba Hari Dass).
Sense withdrawal (Pratyahara): "Pratyahara is the liberation of the senses from the objects that attract them" (Baba Hari Dass). Attention flows inward.
Concentration (Dharana): When the attention is drawn inward, it must be directed toward one object of concentration. The practice is to maintain a narrow gaze on one particular physical or mental object without deviating.
Meditation (Dhyana): Refined Concentration. One uninterrupted flow of attention toward one point.
Samadhi: The perception of a distinct observer and observed dissolves, and all that remains is a contentless Awareness, which is Peace.