I will more directly answer your question. In general, I do not correct people's uses of grammar. I guess I do this for three reasons: in most situations I would be rude in providing the correction; I can't always definitively say for sure that I know the person is incorrect or can't site a source to back up my thinking; and I'm more in the "descriptive" category in my thinking about the use of language -- if I'm confident I've understood the meaning the speaker intended to convey, I'll let the complexities of grammar go.
In formal speaking and writing situations, I know grammar errors can lessen the value, in many listeners' opinions, of the ideas being expressed, so I will privately suggest changes.
All that said, I also use a great deal of non-standard English when I speak, and even when I write:[ul][li]I use
y'all in both speech and writing to disambiguate between singular and plural[/li][li]I use
ain't, but only in speech and exclusively with the pronoun
I[/li][li]I accept
they as a gender-inspecific singular pronoun (though I don't like it much)[/li][li]I do not accept as absolute the old rule of not ending sentences in prepositions[/li][li]And English is a Germannic language, dammit, not a Romance language, I'll split an infinitive if I want to.[/li][/ul]
Besides, even Shakespeare broke the rules when it suited him.
Want to ask the best questions? Read Eric S. Raymond's essay "
How To Ask Questions The Smart Way". TANSTAAFL!