Niyama - the second step of the Raja Yoga (Yama - Self-control, Niyama- Discipline, Asana - Physical exercises, Pranayama - Breath exercises, Pratyahara - Withdrawal of the senses from external objects, Dharana - Concentration, Dhyana - Meditation, Samadhi - Complete Realisation) consists of five principles:
Shauca - Purity
Not only external purity, but more importantly, inner purity. Our clothing, our body, as well as our thoughts and feelings should be pure. The same holds true for the people we associate with. For our spiritual development it is of great benefit to keep good company of people who impart a good influence upon us, who are spiritual and support us with their wisdom.
Santosh - Contentment
Contentment is the greatest wealth we are able to possess. The Indian poet Tulsidas, said: “You may possess mines of gold and precious stone, but inner discontent destroys all wealth”. We can attain contentment only when we recognise that all worldly goods bring disappointment and that inner wealth provides more happiness than material possessions.
Tapa - Self-Control, Self-Discipline
In life, when we encounter adversity and obstacles, we should never give up. Rather we should continue on our chosen path with firm determination. To continue to practice, with self-discipline, patience and perseverance - this is the key to success.
Svadhyaya - Study of the Holy Scriptures
As Yoga aspirants we ought to acquaint ourselves with the traditional scriptures of Yoga philosophy, such as the Bhagavad Gita, the Upanishads, the Yoga Sutras of Patanjali, etc. These scriptures impart valuable knowledge and provide great assistance on our Yoga path.
Ishvara Pranidhana - Devotion to God
Hand over all that you do to the Divine Self with pure devotion. God protects all who surrender with trust and faith.
http://www.yogaindailylife.org/esystem/yoga/en/170300/the-four-paths-of-yoga/raja-yoga/#Niyama