“All who are under the training of God need the quiet hour for communion with their own hearts, with nature, and with God. In them is to be revealed a life that is not in harmony with the world, its customs, or its practices; and they need to have a personal experience in obtaining a knowledge of the will of God. We must individually hear Him speaking to the heart.
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When every other voice is hushed, and in quietness we wait before Him, the silence of the soul makes more distinct the voice of God. He bids us, "Be still, and know that I am God." Psalm 46:10. This is the effectual preparation for all labor for God.” –Ellen White, Ministry of Healing, pg 58

Types of "speaking to the heart":
Hearing Words / Words coming to mind
Pictures
Seeing words
Feelings
Scriptures
Songs

“Since the ministry of the Holy Spirit is of vital importance to the church of Christ, it is one of the devices of Satan, through the errors of extremists and fanatics, to cast contempt upon the work of the Spirit and cause the people of God to neglect this source of strength which our Lord Himself has provided.” -EW, Intro to GC vii-viii

Steps to Hearing God's Voice:

1. Give Him time

2. Write down what you hear

3. Act, erring on the side of loving faith