Grammar vs. Style

[Auldglory]

As I have never been trained as a teacher, I want input from some of the English teachers here on this:

The topic of grammar and style is one on which many a book has been written. In truth, the only way I know the difference between a stylistic problem and a grammatical problem is familiarity with the rules. Truly, one of the more frustrating things that has happened to me was learning that some things (such as the Oxford comma -- that is, the comma preceeding the word "and" in items in a series) were hard and fast rules, when in reality they were only points of style.

Then there is the idea that there are no grammar rules -- only conventions. Think briefly of the future tense of the verb "to be". There once was a point when the convention was to use "shall" with first person singular and first person plural pronouns -- using "will" with either of these was heavily frowned upon.

There is another convention that is quickly moving from being a point of grammar to a point of style: ending sentences with a preposition.

Basically, what I am asking is this: how do y'all handle this tricky topic?
Or do you even address it?

[Iwanna]

To some extent, a grammar rule itself just characterizes some conventiion in a language.