Training Newbies
First thing, if you have never been to the range with the person, take them to the classrom. I have taken people I know to have been Marines, and I still insist on it. Teach them the four rules then tell them about sight alignment and sight picture.
Next, when you arrive in the lane, demonstrate trigger discipline using an unloaded pistol. I demonstrate sighting in and never pointing down the line. I show them that they are to fire, then place the pistol muzzle downrange, and step back.
Then it is their turn. But with an unloaded weapon. Have them pick up, sight in, remove the safety, put their finger in the trigger guard, slow squeeze, click, set the pistol down.
And now the first round. Same as above but with one and only one round in the magazine. That way they can totally freak after the bang, and chuck the weapon downrange, and no one has another orifice installed.
If all goes well, then they get the full mag.
At this point you should have been no more than a foot from their shoulder. Yes it looks gay, and you will be in their personal space. You can watch closely and stop them from doing something stupid.
No one has ever pointed a weapon down the line when I have taught them.