Or simply ignore the stepped approach and caution the first one that crosses your line.....the others will soon learn.
Why give them 4 or 5 bites of the Cherry before using the lemon?
@Padfoot - yes, you can caution, but the point of the thread was for other game management skills. If it is dissent, then it has to be a YC, but there is a level below which new referees need to learn the skills gown to manage!