God speaks through His Word, "I will instruct thee and teach thee in the way which thou shalt go" (Ps. 32:8). That is why we should study the Bible on a regular basis, and ask questions in small group settings. Jesus says, "My sheep know voice (John 10:14)." We know the voice of God by studying the Word of God. God speaks through providential means, that is, through timing. Sometimes God's timing is so profound that we know instantly, beyond a shadow of a doubt that it is the voice of God because no one could have done it but Him. He puts people in our lives at just the right time in answer to prayer.
God speaks to us through the Holy Spirit, "For it is not ye that speak, but the Spirit of your Father which speaketh in you" (Matt. 10:20).The Holy Spirit is the Spirit of God in us. The Holy Spirits comforts, teaches, convicts, helps, and warns us. This why we should not lie, grieve, quench, resist, insult, or blasphem the Holy Spirit, nor conduct ourselves in ways contrary to the will of God.