When I think I "hear" God, it's not a voice, per se. It's a Bible verse that stands out, or a song lyric that stands out, maybe even just a sentence from a secular book. Lately I keep thinking about a phrase I heard when I was reading about the Miraculous Medal: "The graces for which we forget to ask." I think about it at least once a day, I can't seem to put it aside. This to me seems to be God telling me I need to learn more about asking for things from Him. Another instance I had is when I was at a Vocare retreat years ago and someone was giving a talk about God's call. I had been thinking about becoming a teacher, but I wasn't sure if that was what I was meant to do; I had a lot of self-doubt. Then while the person was giving her talk, I heard her say, very clearly, "Answer your call." It was as if she was speaking directly to me. For days after, all I could concentrate on was "Answer your call." Ever since then, I have been moving towards becoming a teacher, feeling that this is what God wants me to do.
So I guess my question for anyone who wishes to answer is, how do you know when it is God speaking to you, and not your own.. subconscious, I suppose, getting in the way?