God doesn't make us responsible for Him to speak to us first. God speaks first. He spoke through Creation so that he'd be obvious.

The first way we start to understand how God speaks is by studying the Bible. It's the "universal voice of God". He made it clear to the prophets that he doesn't come in a booming voice, he comes in whispers.

You know it's His voice if it's consistent with The Bible and it draws you to something that would be like god to do. Just say yes! If we practice that, we cultivate a sensitivity to his voice.