Once the German devotee Uttama-shloka Dasa came to Shrila Prabhupada with an important question that had been burning in his mind for a long time:
"How can I chant with full attention?"
Shrila Prabhupada´s answer was brief and powerful:
"Just try to hear yourself chant sincerely."
I strongly recommend you try this "formula." It will quickly arrest the wandering mind and bring it into a devotional space. From there, you can easily chant with a sense of relationship to Shri Shri Radha Krishna, and then address Them with feelings.
H.H.Sacidananda Swami