There are four methods to attain liberation in Shaivism. They are Anu Upaya, Shambhava Upaya, Shakta Upaya and Anava Upaya. Shakta upaya is also known as Jnana Upaya because knowledge plays an important role in this path.
Shakta Upaya is defined in Malini Vijaya Tantra (II.22) as
When an aspirant with one-pointedness of mind apprehends that reality which is not within the range of utterance (gross or subtle), and thus obtains absorption in consciousness, then that absorption in consciousness is known as Shakta - obtained through Shakti.
In Shakta Upaya, one has to resort to divine consciousness for realization. Divine consciousness is known as Chit Shakti and therefore the method is called Shakta Upaya.
In the Shakta Upaya, the main attempt of the initiate is to realize the self through knowledge. Meditation and contemplation over the identity of the individual and the universal lead to self realization. Through purification of the determinate ideas pure knowledge is aroused in the self.
One has to contemplate some idea or assimilate some truth by thinking about it over and over again. [Abhinavagupta in his Tantraloka (I.148)]
It is difficult for students on the path to become free of the determinate ideas. The solution to this, as suggested in Shakta Upaya is to catch hold of one pure knowledge. That will prove to be veritable boat by which one can cross the turbulent waters of phenomenal existence and safely land on the certain ground of reality.
Regarding impure idea or knowledge Abhinavagupta clearly explains in his Tantrasara (IV), that they are wrong conceptions, which are binding in nature. It is the cause of worldliness or rebirth. Therefore, when a pure idea arises, it dispels the cause of transmigratory existence. So impure idea relates to the idea of the usual, psychological, empirical self. I am thin, weak, ignorant, etc are examples of impure ideas.
About pure knowledge, Abhinavagupta explains in Tantrasara (Chapter IV) that it is the idea and belief that one is an expression of one’s own power. The practice of this pure knowledge is Shakta Upaya.
Regarding the true utility of pure knowledge, Abhinavagupta says it removes the sense of duality, which is ignorance of one’s essential nature.
Consciousness of Shakti is the guiding principle in Shakta Upaya. Shakti assumes the form of a mantra (mystic syllables).
The mind of the aspirant is so intensely identified with the deity of the mantra that is becomes that mantra itself.
Every mantra leads back to that divine consciousness of self, which is the creative Shakti of the Supreme. That consciousness of self is not speech, but the source of all speech, thought and objectivity.
Pure knowledge means pondering over that full, divine I-consciousness as our real self. Since that consciousness is the Shakti of Shiva, pondering over the Shakti is Shakta Upaya, which brings about the absorption of the individual self in the divine self of Shiva.
Shakta upaya is purely a mental yoga. Japa, dhyana, bhavana (devotional attitude), ekagrata (concentration) and so on, fall into this category.
One purpose of dhyana is to acquire supreme powers (Shakti). Abhinavagupta explains dhyana in his Tantraloka (I.89-90).
Japa is also quite essential in this process, i.e., with dhyana. The constant mindfulness of the real nature of Paramashiva, which is beyond words, is japa.
In this process, true directing one’s thought in a particular way, imagining oneself to be in a particular mode.
Source - Some of the above notes taken from Encyclopedia of Hinduism Volume IX (IHRF). (page 88)