Where you feel it first
Everyone has a first signal and it is physical. Not a thought. A thing the body does.
For some people it is the jaw. For some it is heat rising up the neck and into the face. For some it is the hands, or a tightening across the chest, or a change in the breath. A lot of people report that their vision seems to close in on the person in front of them and the rest of the room goes quiet.
Yours is probably the same one every time. You have just never been asked to name it. Finding it is not a technique and it will not calm you down. It is the cue, and without a cue nothing else in this course has anywhere to attach.