The Sanskrit word Niyama refers to the "observances" of an individual in relationship to the world. In many ways, Niyama is directly related to the first step of yoga, Yama. While Niyama may exist in an individuals journey without Yama, they both exist to regulate the other in some ways. It could be said that Niyama gives specific examples of the Yamas. Of major importance in my own life as I study yoga (though I do not actively perform all of it's physical components), is the reality that yoga is in many ways equal parts physical and spiritual. Often, in the Western world yoga is perceived either strictly as an exercise routine (go to your local gym and find they offer classes in "yoga", though it is strictly physical in nature). In some other sects, particularly to those who are opposed to Eastern philosophical teachings and ideas, yoga may also be perceived as a strictly spiritual experience which may be contradictory to other Western religious ideologies. It is undeniable that both of these perceptions are inaccurate, and do no justice to the concept of yoga. Yoga is much more complex than simply one or two concepts that many pessimistic and close-minded individuals like to pigeonhole it into.
With that said, let me provide for you information on the ten traditional Niyamas.
The ten traditional Niyamas:
Hri: Remorse, being modest and showing shame for misdeeds.
Santosha: Contentment; being satisfied with the resources at hand - therefore not desiring more.
Dana: Giving, without thought of reward.
Astikya: Faith, believing firmly in the teacher, the teachings and the path to enlightenment.
Ishvarapujana: Worship of the Lord, the cultivation of devotion through daily worship and meditation, the return to the source.
Siddhanta shravana: Scriptural listening, studying the teachings and listening to the wise of one's lineage.
Mati: Cognition, developing a spiritual will and intellect with the guru's guidance.
Vrata: Sacred vows, fulfilling religious vows, rules and observances faithfully.
Japa: Recitation, chanting mantras daily.
Tapas: The endurance of the opposites; hunger and thirst, heat and cold, standing and sitting, and any other opposite forces.
I would like to just restate that god (and further the "Lord") do not refer to any deity, though I am sure some followers of yoga with a religious background may follow it in such a way as this.