Don't be shy with new shooters.
And don't be harsh, either.
The approach that always seems to work is to kind of mosey over behind them and say, "Can I show you how to do that better"?
Never had a refusal, yet.
And you will usually get all their brass, too.
Walt Kelly, alias Pogo, sez:
“Don't take life so serious, son, it ain't nohow permanent.”