Question - "Well, what is the rule for concentration? Where should one concentrate?" Sri Ramakrishna : "The heart is a splendid place. One can meditate there or in the Sahasrara. These are rules for meditation given in the scriptures. But you may meditate wherever you like. Every place is filled with Brahman-Consciousness. Is there any place where It does not exist? Narayana, in Vali's presence, covered with two steps the heavens, the earth, and the interspaces.* Is there then any place left uncovered by God? A dirty place is as holy as Ae bank of the Ganges. It is said that the whole creation is the Virat, the Universal Form of God. There are two kinds of meditation, one on the formless God and the other on God with form. But meditation on the formless God is extremely difficult. In that meditation you must wipe out all that you see or hear. You contemplate only the nature of your Inner Self. Meditating on His Inner Self, Siva dances about. He exclaims, 'What am I! What am I!' This is called the 'Siva yoga'. While practising this form of meditation, one directs one's look to the forehead. It is meditation on the nature of one's Inner Self after negating the world, following the Vedantic method of 'Neti, neti'. "There is another form of meditation known as the 'Vishnu yoga'. The eyes are fixed on the tip of the nose. Half the look is directed inward and the other half outward. This is how one meditates on God with form. Sometimes Siva meditates on God with form, and dances. At that time he exclaims, 'Rama! Rama!' and dances about."
God has kindly made it very easy for us to chant and meditation His names, and He has also invested all His powers in them
Where should one concentrate?" --- One should concentrate on the Holy Names of the Lord, the beautiful form of the Lord and the Pastimes of the Lord. what is the rule for concentration? --As the nature of the mind, it will wander off into different thoughts, but don't focus on those thoughts. Simply draw your mind away from those thoughts and place it on the Lord. Gradually this process of focusing on the Lord will help to improve the concentration on the Lord.