First we must recognize an audible voice is only one way in which God speaks to us. God speaks to us through other people, the the Scriptures, through our thought lives. We can have times when we keep seeing the same message showing up in various places and ways. God communicated with us through dreams and visions, as well as through movies and books other than Scripture. We must not limit the ways God can speak to us. Still we are left to ponder how do I know what is God communicating and what is something else.
Our great challenge is we might not ever know 100%. However, there are some activities we can employ to test what we think God is telling us. The most effective way to test is through the regular practice of spending time with God. Romans 12 instructs us to be transformed by the renewing of our minds, and then we will be able to test and approve God's leading. The transformation requires an investment of time and effort, training ourselves to be in conversation with God.
When there is a specific leading we want to test form our ongoing conversation with God, the first stop is the Scriptures. God will not call us in a direction that is contrary to what has been offered to us in the Scriptures. If we are feeling lead in a direction, yet it does not line up with the Scriptures, we can know this is not a leading of God, but from some other place or person. After the Scripture alignment test, we move to the test of community. While each of us must decide personally what we are going to do with Jesus, there is nothing private about our journey. Following God through Jesus Christ is always to be done in the context of community. When feeling a leading from God we are to test the leading with a community of believers whom we trust to speak truth and offer good counsel. This must be a group of people whom you trust and have an ongoing relationship with. If these folks reach consensus about the leading of God, this is another positive.
The next step requires the most risk, go. Once you have tested the leading or communication from God with the Scriptures, and have trusted your community, step in faith. At this point there is still no guarantee you have heard God or not. However, you have employed some steps which help increase the probability greatly. Once you take the step of faith it is imperative to remain in conversation and connection with God and your community. This will allow for mid-course correction or a complete all stop in the event it becomes evident our understanding of God's leading has missed the mark somewhere.
Many people get paralyzed waiting to be sure what they feel, think, hope and dream are from God. They will spend their entire live wanting to make sure they have it right before they take action. This is a great tragedy, and what is killing the witness of Jesus Christ in many places. We are going to get it wrong from time to time, possibly more often than that, yet it is easier for God to use us if we are in motion already. Take a step of faith, if it doesn't work, seek forgiveness where it is needed, repent when needed, keep seeking God, and keep seeking out. The more we engage the process, the more we have conversation with God, the more clear the voice of God becomes. The more clear the leading of God becomes.