There are three golden rules for successful grammar teaching. Unfortunately, nobody knows what they are. So instead, let me offer a few personal opinions. I'll try to be brief: I've spent the last three years writing a practical grammar course that's moving towards publication, and I've got so much in my head that it's hard to sum it all up.
There's a lot of theory around, much of it contradictory. It can be valuable, but I sometimes feel, to quote Mark Twain, that "the researches of many commentators have already thrown much darkness on this subject, and it is probable that, if they continue, we shall soon know nothing at all about it". My rather unhelpful view is that it all (...)
Read more here.