Make sure you're breathing more from your diaphragm, or belly, not from your chest -- that's too shallow. Deep belly breathing allows you to take in more air, which can also help prevent side stitches.
You should exhale through your mouth and try to focus on exhaling fully, which will remove more carbon dioxide and also help you inhale more deeply.
Here are a few more tips for breathing while running:
- Try to take three footstrikes for every inhale, and two footstrikes for every exhale.
- As a beginner, try to run at a pace at which you can breathe easily. Use the "talk test" to figure out if your pace is appropriate. You should be able to speak in full sentences, without gasping for air.
- Slow down or walk if you're running out of breath. If you relax and slow the pace, breathing problems often take care of themselves. Don't overthink it!

