At a club level match I always ask if I have any first time shooters. If I do I give them some assistence. Before they shoot the first stage I give them a bit of a walk through on what to expect at LAMR and ULSC, on keeping their finger out of the trigger guard while moving and reloading and on the 180. I tell them I will warn them once if they have their finger on the trigger when they shouldn't and when the get close to the 180. After that they are just another competitor.
It's a hard call because we want to encourage new shooters but where and when do you draw the line? Do you only tell them the first time or after the second or third? Do you tell them they had a miss or they forgot to shoot at a target? I still make dumb mistakes on stages but that is on me not the RO.