Srila Prabhupada said that attentive chanting means to hear oneself chant. For me, hearing myself chant is easier than trying to fix my mind. I just put all my energy to my ear and I try to listen and the mind also becomes more focused.
(Kadamba Kanana Swami, 04 April 2015, Durban, South Africa, Ratha Yatra Lecture: The Golden Incarnation)
But, another way to come to attentive chanting is to become more attracted to Krsna. The more we hear about Krsna, his wonderful qualities and his wonderful pastimes, the more we find out about Krsna, the more we become attracted to Krsna. As Srila Prabhupada explains, this chanting is not an artificial imposition of the mind. So ultimately, it is not about forcing the mind to think about Krsna. That is only the beginning. After we find out more about Krsna, after we become more attracted to Krsna, we will naturally get drawn towards Krsna. In that way, as we get more and more attracted to Krsna, we get more and more attracted to chanting. Then attentive chanting becomes a natural thing.
So that is where it has to go. We can think about that and in the meantime we try, as an exercise, to hear ourselves chant. In that way, the mind will shrink..