On my way in to work this morning, I passed an accident; a pedestrian had been hit by a car and was lying in the middle of the street (with the usual crowd of concerned gawkers). And one of them--the gawkers, that is--was kneeling next to him, checking him for broken bones. All of which is fine, and at first I thought the helper must be an off-duty EMT or a fireman from the station that's less than a block away, except that he moved the guy's head. I am not a paramedic nor a medical professional of any sort, but I'm fairly sure that first rule of checking the trauma victim is don't move his head. Because it's possible that he had some sort of neck injury that was OK as long as he stayed still, but that could, oh, say paralyse him if it got moved wrong. That's what the collar and backboard is for--to keep his head from moving.
There is nothing bad about wanting to help, but for God's sake if you don't know what you're doing don't help.