Samprajnata is achieved through reflecting on the world and the yogi’s position in it while meditating. In this way, one eventually comes to the realization of one's true Self and becomes aware of Brahman as the ultimate Reality.
Unlike with asamprajnata (unconscious meditation), in samprajnata the yogi is aware of his/her own individuality, as well as the presence of other objects around him/her.
There is no simple or quick route to achieving samprajnata. This state can be regarded as one of the ultimate goals for anyone who is serious about meditating to enhance the spiritual aspect of a yoga practice.