Lalalalalalaa! ♪
There's a lot of things you might hear in your head. Sometimes it's yourself, your consience, temptation, ect. But I don't think hearing God's voice is a problem, but rather descerning His voice past all the rest. I think the more you read God's word is the more you start to understand God's character. And the more you understand his character, the more you can tell what's God and what's not. So read about how Jesus talked, how Jesus got frustrated, how Jesus loved. Don't just read, but study. It's really as simple as that, I guess.
And when you hear a tugging in your heart that's chalenging you to step out and give someone something for no reason, or ask them how they're doing or sit with them, and you might wonder if you're being silly or God really does want you to do that, than just know; if you do it no matter what, God will be sooo blessed and so proud of you, even if it's not what he said. If Jesus would do it, than you will most certaintly be rewarded.