What to do after someone passes out?

You should help them, also tell them they are ok but they have fainted.

Lay the fainted person on his/her back and elevate the legs (Use a chair or a bench). Check for a pulse (if there is a pulse still read on) either one you need to open the airway, if not begin CPR (give 3 breathes into the mouth, and 30 pumps to the chest, check for pulse and repeat) But before you begin CPR call 999/911/000 etc and ask for emergency help, follow the rest of that and you should be fine, If none of the above work, if the person is breathing put alcohol under nose.