While meditating on your Ishtadevatha, if you can’t visualize that form in your mind, continue the meditation and recite the Holy names of that Ishtadevatha

Nama Article 21st Jun 2016

BHAGAVATHA DHARMAM - First Skandham - Swami Abhedananda

Worship all forms of God. But remember that all are different forms of the one and only God. While worshipping different forms of God, remember only your Ishtadevatha (that form of God which appeals to you most) 

While meditating on your Ishtadevatha, if you can't visualize that form in your mind, continue the meditation and recite the Holy names of that Ishtadevatha.

Chant the Mahamantra Nama kirtan :

Hare Rama Hare Rama Rama Rama Hare Hare
Hare Krishna Hare Krishna Krishna Krishna Hare Hare