Niyama– the Yoga Upanishads Explains

Niyama refers to internal disciplines or observances — the personal commitments for a disciplined and pure life. It helps purify the body, mind, and heart, making one ready for deeper yogic practices like pranayama and dhyana (meditation).
Niyama – Penance, contentment, belief in the existence of the Supreme Being, munificence, the adoration of Hari or the all-pervading Vishnu, the study of the Vedanta system of Philosophy, modesty, determination (arriving at right conclusion), silent prayer (Japa), and austerity (Vrata).
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1. Penance (Tapas) – Tapas are Emaciating the body (religious penance), Expiatory penance and like.  Reduction of body, by observing the Krcchra and Candrayana austerities and the like, prescribed by Holy Writ, is known as Tapas.
2. Contentment (Santosha) – Contentment with whatever chance brings in is what is termed as Santosa. The pleasure is derived by people in their everyday life by the accidental acquisition of any gain. One devoid of all attachment gets out of detachment till the moment he realizes the Brahman, that they know as Supreme Contentment.
3. Belief in the existence of the Supreme Being (Astikya) – Right belief in the lines of Dharma and Adharma as laid down by the Vedas, is known as Astikya. Faith in the Shruti and Smriti is belief in the existence of the Supreme.
4. Munificence (Dana) – The giving away of wealth earned by righteous means, in all sincerity, to the needy or whatever else is bestowed.
5. Worship of Ishvara (Ishvara Pujana) – The worship of Vishnu, Rudra and other deities, as far as resources would permit, with a cheerful disposition, is known as Ishvarapujana.  A heart free from passions, speech not rendered bad by falsehood and the like, action devoid of violence; that is the worship of Ishvara.
6. Study of the Established Truth (Siddhanta Shravana) – Study of the established Truth expounded in the Upanishads. Investigation into the true import of the Vedanta.
7. Disinclination towards action, considered base according to the Vedic and worldly standards of conduct, is known as Hri.
8. Faith (Mati) – Confirmed belief in all things enjoined by the Veda is known as Faith.
9. Prayer (Japa) – The practice of Mantras, not running counter to the injunctions of the Veda, in accordance with the initiation of the Guru and in keeping with the prescribed rule, is known as Japa. Practice of the Mantra is known as silent prayer. Prayer is said to be two kinds, that by word of mouth and the mental one. Mental prayer is two-fold assuming the forms of ruminating (Manana) and meditation (Dhyana). Prayer uttered low is a thousand times more efficacious than prayer uttered loud. Loud prayer would bestow fruits on all, as prescribed in the Scripture. If the Mantra is heard by the ears of the low classes, it becomes devoid of efficacy in bearing fruit.
10. Austerity - Constancy in observance of the injunctions and prohibitions laid down in the Veda, is known as Vrata.

 
Nine-fold Niyama –

1. Devotion to the Guru (who dispels the darkness of the pupil’s ignorance with torch of his superior knowledge);
2. Attachment to the path of knowledge leading to the truth (of Brahman);
3. Enjoyment of the real substance (of the Brahman), which is easily accessible in the form of the extreme bliss, through the grace of the Veda and the preceptor;
4. Supreme satisfaction at such enjoyment of the real substance;
5. Complete detachment from even such satisfaction;
6. Abiding at a silent, secluded and solitary spot, (by effectively controlling mind in the desolate place, by controlling the mind at a place whether inhabited or desolate, with effort, and by controlling the mind at such a place without any effort);
7. Mental inactivity with the firm conviction, that there is no mind apart from the Brahman;
8. Non-desire towards the fruit of one’s actions;
9. Detachment resulting from revulsion from everything other than the Atman.