Patanjali's writings influenced what would become known as Ashtanga Yoga, or the "Eight-Limbed Path." This path, which encompasses both spiritual and material elements, is fundamentally the guideline of what yoga is and in some ways where the focus of yoga should be. There are eight steps, however they are not necessarily intended to be followed in any specific order. It is completely relative to culture and even more subjectively dependent on the individual. The eight limbs are listed and lightly described as follows:
1. Yama (the "moral" guideline): non-violence, non-lying, non-covetousness, non-sensuality, and non-possessiveness.
2. Niyama (the five "observances"): purity, contentment, austerity, study, and surrender to god*.
3. Asana: The physical process of yoga
4. Pranayama The control of life force
5. Pratyahara ("Abstraction"): Withdrawal of the senses
6. Dharana ("Concentration"): Fixing the attention on a single object.
7. Dhyana ("Meditation"): Intense contemplation of the nature of the object of meditation.
8. Samadhi ("Liberation"): Associated with death of the body and finding the true self (Atman)
*god is not a religious god, but is named "Brahman" in Sanskrit. The concept of this "god" is that since "god" is everything (and inadvertantly unable to be less than all things), he contains all aspects of the world. This concept extended merges the idea of the true individual self (Atman) with the idea of an all-being god (Brahman). In yoga, Atman is Brahman. All yogis (doers of yoga) are inadvertantly a part of everything, and inadvertantly apart of this god. The focus of yoga is to reach the point where the individual becomes one with this true self (typically through the death of the physical body).
You can expect future articles detailing the specific limbs in more detail!