After detaching the mind from the world, and before surrendering to God, there is need of a divine entity, without whom one cannot attain the Supreme goal. That entity is a God-realized Saint or Guru. It is the Guru, who decides which path is best for each devotee to surrender to God. Again, it is he who dispels all doubts faced by the aspirant on the path. Mere detachment is not enough to attain God.
The Bhagavad Gita states:
tadviddhi praṇipātena paripraśhnena sevayā upadekṣhyanti te jñānaṁ
Shree Krishna says to Arjun, "Learn the Truth by approaching a spiritual master. Inquire from him with reverence and render service unto him. Such an enlightened Saint can impart knowledge unto you because he has seen the Truth.”
The Ramayan also says:
guru binu bhava tarai na koī”; “guru binu hoī ki jñāna”
“Without the guidance of a Guru, one cannot cross over the ocean of material existence.” Again it says, “Without the guidance of a Guru, one cannot attain the knowledge of God.” Thus, the unanimous view of all scriptures is that we must surrender to a Guru in order to know the unknown entity called God.
Watch this video lecture by Shree Maharajji on the topic, "Who is a Guru" with