James Doty calls this, "Ruth's Trick #2." Ruth is the woman Doty met when he was twelve who showed him these techniques.
I should mention that this is a very basic meditation technique. If you've downloaded the "10 Percent Better" App, you're further along the road. But this is a very clear explanation of how to quiet your mind.
1) Once your body is relaxed (Ruth's trick #1) focus on your breath.
2) It is common for thoughts to ariase and for you to want to attend to them. Each time this occurs focus specifically on your breathing. Some find that when they actually think lf their nostrils and the air entering and exiting that this brings their focus back.
3) Other techniques that assist in decreasing mind wandering are the use of a mantra, a word or phrase that is repeated over and over, or focusing on a candle or single object. By doing so it is impossible to give those wandering thoughts attention. In some practices, the teacher gives the mantra to the student who tells no one else the mantra. Find that which works best for you. Everyone is different.
4) It will take time and effort. Don't be discouraged. It may take a few weeks or even longer before you start seeing the profound effect of a quiet mind. You wont have the same desire to emotionally engage in thoughts that often are negative or distracting. The calmness you felt from simply relaxing will increase because when you are not distracted by internal dialogue the associated emotional response does not occur. It is this response that has an effect on the rest of your body.
5. Practice the above exercise for 20-3- minutes per day. Make the time."
A small sidebar: I have tried to meditate since I was nineteen. I've had periods when I pursued this and was able to meditate for about an hour. Right now, I can meditate for about twenty minutes. YOUR MIND WILL CONSISTENTLY WANDER. You think about something, then bring your focus back to your breathing. I literally do this OVER A HUNDRED TIMES IN A TWENTY MINUTE PERIOD. And every time I return to my breathing, it's like one pushup for my brain.
Do this. Get the App, if you need. And do this.