Find somewhere quiet to sit for about 15 minutes each day (when you're more advanced at meditation you can do it anywhere: at your desk at work, on the bus, etc, but it's good to start somewhere without many distractions). Close your eyes and take deep breaths all the way down into your belly. Focus on your breathing. When you find distracting thoughts coming into your head, acknowledge them but do not focus on them. Return to your breathing by saying to yourself "Breathe in, breathe out."
