A calling

How do we know what we are meant to do? Ok, tough question, or maybe not written well, but how do we know where God wants us to go and what to do? I realize that someone's going to answer that when we are quiet enough, we will hear what God wants. I know that's true, but sometimes I have trouble making the step to understand if that's my mind imposing something that I think is a calling. How do other people discern what's a real calling versus their mind just "playing" with them?