The right equipment, training and running route isn't always enough to ensure a good run, especially if your breathing is all over the map. To help stabilse yours, try incorporating a set inhale-exhale ratio.
Photo by aarmono.
The aptly named Complete Running Network details how to breathe properly when running. Included in their list of seven tips is the importance of establishing the right inhale/exhale ratio. Specifically, they suggest that runners should take three footsteps for every inhale and two footsteps for every exhale, which puts them at a 3:2 ratio.
This means you INHALE on the LEFT, RIGHT, LEFT foot strikes and EXHALE fully on the RIGHT, LEFT foot strikes. This pattern is not that hard to turn into a habit, but it may require you to slow your pace down for a few runs to master the technique. You will notice a lower heart rate as you are able to get more oxygen in and more importantly push all the carbon dioxide out of your body. You may notice that you naturally drop to a 2:1 ratio when you are really pushing it to the finish. That is OK.
The article also says that to help remove more CO2 from the lungs, more focus should be placed on exhaling fully than on the inhale, and that the breaths should come from your diaphragm rather than your chest (where the breathing is more shallow). Once you have your breathing down pat, you may even want to try ditching your shoes for an even better run.
How to Breathe When You're Running [Complete Running Network]