How do you check to see if a unconscious person is unconscious?

You check for a pulse on their left side of the neck, their wrist or you check for breathing- although normally you'd do all of them.

Tap the person and ask "Are you okay?"

tap on their shoulders and repeatedly ask if they are OK. if no response they are most likely unconscious.

fist check for and danger then speak in each ear a bit loud are uOK if there is no reply then shake them lightly by the shoulders if there is still no reply check if airways are blocked by opening...

Go to sleep.