This is a great question, and one that should be especially considered by one who professes to be a Christian. Let's face it. There is no shortage of conflicting thoughts among Christians on just about anything, but especially with regards to faith and morals.
Today, our world is full of noise and "busyness". Add in the fact that decades of media and political slants have been rather successful at diluting at best and manipulating at worse the "messages" we receive, and it is a little more clear why it has become more difficult for us to discern the "voice" of God in our "hearts".
This is a good place to start. To be able to recognize God's "voice", we must first understand that He speaks to the "heart", the depths of one's being. It is where God has already written His law. (Romans 2:14-15) It is in the heart that "conscience" must delve to seek out God's true voice.
For when the Gentiles who do not have the law by nature observe the prescriptions of the law, they are a law for themselves even though they do not have the law. They show that the demands of the law are written in their hearts, while their conscience also bears witness and their conflicting thoughts accuse or even defend them. Romans 2:14-15
Conscience is the judgement or reason by which one weighs the moral merits of one's actions. The Christian understands it as something more though. Cardinal Newman described conscience as a "messenger" of God, which "speaks to us behind a veil".
[Conscience] is a messenger of him, who, both in nature and in grace, speaks to us behind a veil, and teaches and rules us by his representatives. Conscience is the aboriginal Vicar of Christ. John Henry Cardinal Newman, "Letter to the Duke of Norfolk," V, in Certain Difficulties felt by Anglicans in Catholic Teaching II (London: Longmans Green, 1885)So God speaks to us in our hearts where He has written His law and gives us conscience as a messenger to "interpret" for us so that we are equipped to always do right, right? Equipped, yes, but owning (or being equipped with) high priced power tools doesn't make you a master carpenter. There's training involved, lots and lots of training.
In fact, continuing with the carpentry theme, the Christian recognizes that while one's "skills" (or ability to recognize God's voice) increases, his or her stint as a "journeyman" is truly a lifelong apprenticeship.
Next time, I will begin to address this training of or the "formation" of conscience.