Don't try to quieten your mind... that just adds more "noise" and pushes the quiet further away.
Just let the stuff that's happening go away on its' own. Listen to your breath. Don't try to "not listen" to the other stuff ... just don't dwell on it and get hung up on it.
Lots of people try to put themselves into a state where everything is "shut down" and is calm or quiet. My zen teacher always called that "putting yourself to sleep while awake."
I think the state we can approach is "alive, awake, aware, and free." When we can really focus and put our attention where we choose, the extraneous stuff just quiets on its own.
Breath and pay attention to what's happening!