Siddhi powers are said to be obtainable by meditation, control of the senses, devotion, herbs, mantras, pranayama, or good birth.
There are Nine main siddhis
In the Puranas there are nine forms of Siddhis (supernatural powers). They are:
Parkaya Pravesha: Parkaya Pravesh means one’s soul entering into the body of some other person. Through this knowledge even a dead body can be brought to life.
Haadi Vidya: This Vidya or knowledge has been mentioned in several ancient texts. On acquiring this Vidya, a person feels neither hunger nor thirst, and can remain without eating food or drinking water for several days at a stretch.
Kaadi Vidya: Just as one does not feel hungry or thirsty in Haadi Vidya, similarly in Kaadi Vidya a person is not affected by change of seasons, i.e. by summer, winter, rain, etc. After accomplishing this Vidya, a person shall not feel cold even if he sits in the snow-laden mountains, and shall not feel hot even if he sits in the fire.
Vayu Gaman Siddhi: Through this Siddhi a person can become capable of flying in the skies and traveling from one place to another in just a few seconds.
Madalasa Vidya: On accomplishing this Vidya, a person becomes capable of increasing or decreasing the size of his body according to his wish.
Kanakdhara Siddhi: One can acquire immense and unlimited wealth through this Siddhi.
Prakya Sadhana: Through this Sadhana a Yogi can direct his disciple to take birth from the womb of a woman who is childless or cannot bear children.
Surya Vigyan: This solar science is one of the most significant sciences of ancient India. This science has been known only to the Indian Yogis; using it, one substance can be transformed into another through the medium of sun rays.
Mrit Sanjeevani Vidya: This Vidya was created by Guru Shukracharya. Through it, even a dead person can be brought back to life.