The sadhana of inner concentration consists in:
(1) Fixing the consciousness in the heart and concentrating there on the idea, image or name of the Divine Mother, whichever comes easiest to you.
(2) A gradual and progressive quieting of the mind by this concentration in the heart.
(3) An aspiration for the Mother’s presence in the heart and the control by her of mind, life and action.
Ref : Letters on Yoga Vol. II