From an Australian (or more specifically Queensland) perspective, this is what I tell our guys (more or less - this isn't a script I use, but the general tone of it).
What players say can be directed towards four groups: us, the opponents, their teammates or themselves.
If their comments are directed towards us, or towards opponents, our degree of tolerance is low. If there is an obscenity involved, it is a flag. If there is a personal insult involved, you can choose to ask them to repeat it (and if they do, flag them), or you can flag it straight off if severe enough or it looks like the situation could get inflamed if ignored. If it is general boasting or trash talking, a loud reprimand or caution is an appropriate first step.
If they are talking to their teammates, our degree of tolerance is higher. If there is an obscenity that can be heard by a member of the public, it is a flag. Otherwise, it would be hard to justify a flag. If they are verbally putting down an opponent, but not directly speaking to that opponent, a verbal reprimand to tell them that's enough talking should be the first step, loud enough for the opponents to hear that you're warning them. Flag if it continues.
If they are talking to themselves (either through temporary insanity or as a result of an emotional outburst), firstly ask yourself if this is a reaction to an injury. If so, have a very high tolerance level, even if there is an audible obscenity. Otherwise, treat it the same as talking to their teammates.