meditation. breathing exercises. try breathing long and deep when you aren't exercising, say like when you are at home or driving. the maximum lung capacity is usually never reached through normal every day breathing, thus not strengthening the lungs. I did some deep breathing exercises for a while and I got better results on my run time.
try this:
try to breathe slowly so your heart rate is at an idle pace. breathe in deep, and let out air a little at a time. as time progresses, try to hold in the air longer, and exhale at longer intervals.
breathe through the nose, and out through your mouth.