In order to know this intimate place of hearing God by the Spirit, we first must have entered into the union. We must know in experience what Jesus said in John 14:17, "...He (the Holy Spirit) dwells with you, and will be in you." This is not an automatic transaction because we "believe in Jesus." We must believe in Jesus before we will even look to Him to hear what He has to say, but believing in Jesus is not the same thing as being made one with God in the Spirit.
We are made one with God when we are baptized into the body of Christ and made to drink into one Spirit (John 3:5), and thus are now alive unto God--that is, we are aware of God with spiritual senses. To say it another way, our spiritual ears have been opened so that we can now hear God. This is a work of grace in our hearts which is accomplished by the Lord.
We could say that we must hear God in order to even come to a place of repentance and faith, to partake of the Holy Spirit and be made one with God. But the hearing that follows from that point on is a deeper and more intimate place with God. It could be compared to the difference between courtship and marriage. Before a couple is married, the love they experience is real, and the communication greater than in any other relationship. But when they enter into marriage and are made one, their relationship, love, and communication take on a deeper and more intimate dimension than they ever thought possible.