So when I first started having panic attacks, I would usually leave the place -give in to the fight or flight mode- so I would rush to a toilet, or go out to get some air, which is fine/ however sometimes that isn’t possible: e.g when you are in a meeting, when you are in a professional or formal gathering etc.
Then my therapist at that time taught me breathing techniques, didn’t work so well for me.
Then she taught me grounding techniques which actually I have used a couple of times.
So basically it is meant to get your attention to the now and away from the scary panic going on inside your head.
So here is an example - she actually taught me this but I found an example of it on the net- sounds silly when you read it but once you actually do it, it shifts your brain attention to different areas in the brain.