"Prayer" per se is so common among men who believed into God, whichever religion. However, the real significance of prayer is hardly realised even among those prayerful ones. Focusing on the Christian's prayer, even many including me, the understanding of the depth of prayer is so shallow, in fact, too shallow. No wonder, many prayers were never answered. Even if so, most would be out of God's mercy, not according to His heart's delight.
Jude 20 But you, beloved, building up yourselves upon your most holy faith, praying in the Holy Spirit. A genuine prayer is a prayer in the Holy Spirit; which involves God as the Holy Spirit praying through the one who prays.
Ephesians 6:18 By means of all prayer and petition, praying at every time in spirit and watching unto this in all perseverance and petition concerning all the saints.A genuine prayer is a prayer in spirit. This is our regenerated spirit, indwelt by the Spirit of God, the mingled spirit — the spirit that is our spirit mingled with God's Spirit.
Romans 8:16 The Spirit Himself witnesses with our spirit that we are children of God. A genuine prayer is a prayer in the Spirit with our spirit; a mingled prayer; the source and the means pray together for the goal of the source.
1 Corinthians 6:17 But he who is joined to the Lord is one spirit. A genuine prayer is a joint prayer, God and man, praying together in one spirit.
Putting all these verse together, a genuine prayer is a prayer in which God as the source, initiator of prayer, is praying through the praying one, as the means, channel, praying the prayer that is absolutely of God, in God, for God, in oneness with the praying one. Such prayers is always the will of God echoed by man on earth for the fulfillment of God's will. And will always be answered. This kind of prayer is a "joint prayer." God and man praying together as one.
This reminds me of my need to be in spirit in prayer, not praying from my mind, nor emotion, nor will, but in spirit. Exercising my spirit in prayer to pray God's prayer for God's purpose. A joint prayer, a genuine prayer, of God, through God-man, for God.