as for me the thing i find most helpful is breathing technique. when i was a kid i was lucky enough to have learned from a few world class rifle and pistol shooters. i have used their breathing techniques ever since. before every shot i take 2 deep breaths, settle my sights, take one more deep breath in, settle the the sights once again, release HALF of that breath, resettle the sights one last time, squeeze the trigger and follow through. it takes longer to read this than to learn how. the deep breaths also help to even out your heart rate.