The method has three stages and they are always given in order. Shravana is hearing the teaching from a teacher who stands in a line of teaching, which the tradition regards as necessary rather than optional, since the great sentences of the Upanishads are held to do their work when they are received rather than when they are worked out privately. Manana is reasoning on what has been heard until the objections are answered and no doubt remains at the level of argument. Nididhyasana is sustained dwelling on the conclusion until it stops being a conclusion and becomes the way things are seen.
The characteristic instrument is negation. Neti neti, not this, not this, is applied to everything a person might take themselves to be, the body, the breath, the mind, the sense of agency, until what cannot be set aside as an object is what remains.
Shankara school holds that knowledge alone liberates and that action, however scrupulous, cannot, because action produces results and liberation is not a result. The other paths are preparatory on that reading. Other Vedanta schools disagree and give devotion the final place. The modern scheme in which karma, bhakti, raja and jnana are four parallel yogas suited to four temperaments comes from Vivekananda in the nineteenth century and is a systematisation rather than a classical arrangement. Jnana here should also not be confused with the Jain kevala jnana, which names a state attained rather than a method of attaining it.