If you track how many miles you are running, focus on breathing in through your nose and out through your mouth for the first minute of each mile. If you don’t count miles, just breathe in through your nose and out through your mouth the first minute of every 10 minutes or so.
Why? Breathing this way helps you communicate with your diaphragm. It builds more stability in your run and keeps you from shifting from side to side while you stride. Ultimately, this prevents you from wasting energy so you can get the most out of each mile.