Pantanjali created these eight limbs of yoga, which can be used as a general guide to practice yoga and help one to attain union with God. This eightfold path to enlightenment is called Ashtanga Yoga ("ashta" meaning "eight" and "anga" meaning "limbs") Hence the Name Eight Limbs and they include:

YAMA : Conditional yoga behavior, personal and social
NIYAMA : Observances
ASANA : Discipline of the physical body, Postures
PRANAYAMA : Control over bio energy through respiratory action/ Breath Control
PRATHYAHARA: Withdrawal of the senses inwards through abstraction
DHARANA: Concentration
DHYANA: Meditation
SAMADHI: Transconsiousness/ Superconcious

Yoga, practiced in its correct sequential order, gradually leads the practitioner to rediscover his or her fullest potential on all levels of human consciousness - physical, psychological and spiritual. Through this practice of correct breathing (Pranayama), postures (Asanas), and gazing point (Concentration), one gains control of the senses and a deeper awareness of self. Maintaining this discipline with regularity and devotion, one acquires steadiness of body and mind.

Thus Patanjali's eight-limbed approach helps one to gain mastery over our ego-minds, free up our bodies, and access the Higher Self.

The first step then in doing yoga is practicing the Asana (physical exercises), which not only work the body but also train you to relax. The best time to do the yoga postures is about one hour after getting up or in the early evening. Wear loose clothes and make sure you have good ventilation in the room where you exercise. Use one inch thick rug and do not try to do yoga on the bed or on the floor that is hard.

Do not eat and avoid hot shower or bath immediately after yoga, since this draws blood away from the internal organs and glands to go to the skin. Eat after an hour and a light shower after 20 minutes is good.

Asanas are also based on a sound knowledge of human anatomy and physiology. Asanas or postures help us free up the flow of energy in the body. Yogis knew that placing the body in certain positions would stimulate specific nerves, organs and glands

Originally yogis recommended 84 asanas, though there are many variations done today and a dozen of them practiced regularly will give us enough benefit. Few postures/ Poses are named after nature like plants and animals as they were devised by observing the animal in the wild.

The asanas are based on five principles.

Use of Gravity
Organ massage
Stretching
Deep breathing
Concentration

Use of gravity:
The inverted postures such as the headstand, shoulder stand and the reverse posture take advantage of gravity to increase the flow of blood to the desired part of the body; in the headstand to the brain, in the shoulder stand to the thyroid gland and in the reverse posture to the gonads (sex glands)

Organ massage:
The position of the asana causes a squeezing action on a specific organ or gland, resulting in the stimulation of that part of the body.

Stretching muscles and ligaments:
This causes an increase in blood supply to the muscles and ligaments and helps them to relax. It takes pressure off nerves in the area. This stretching is involved in all the asanas, since it has such a beneficial effect on the body.

Deep breathing:
While holding the yoga posture we breathe slowly and deeply, moving the abdomen only (abdominal or low breathing). This increases the oxygen and prana supply to the target organ or gland, thereby enhancing the effect of the asana.

Concentration:
Along with breathing slowly and deeply, we also focus our attention on the target organ or gland. This brings the mind into play, and increases the circulation and supply to the organ or gland. Your mind is less distracted and swayed by external events and you are therefore calmer and worry less. You will also be able to solve day-to-day problems better and have more success in whatever activity you undertake.