This is just one question asked by teachers who feel helpless once encouraged to ditch explicitly teaching grammar. It’s a really good question, and if the answers were obvious, there wouldn’t be as much strife…

Meaning
When the focus moves away from teaching how a language works, we can go straight to meaning. That is, to the reader, it matters less how many prepositions I’m using in this writing, and more the actual content of what’s being expressed. But we can’t really teach meaning, right? We just say things and write things that convey meaning. Teaching, then becomes conveying meaning about something.

Purpose
There needs to be a reason for conveying meaning, and this reason doesn’t have to be complicated. Asking as student if they liked the latest Marvel movie has plenty of purpose; you get to see how popular the movie is, informing you of potential compelling topics that might come up in class. Is there a funny Thanos meme in your target language? That might be instant content to open a class—laughing, or criticizing it together. This is entertainment.

Of course, learning is a natural purpose for conveying ideas. This is school, right? There are things students don’t know, that we can teach. This, then, would be the easiest answer to wrap one’s head around; what to teach? Teach about the target culture.

However…

In teaching about the target culture, begin with topics that interest students, or questions they have about something they might not otherwise find interesting. For example, transportation in Italy might be a boring topic, but if you state that cars are not allowed in Venice, you might create an instant hook. How do people get around? Does everyone have a boat? There are naturally curious details about target cultures that we can guide students to discovering rather than giving them pages of English texts, often filled with boring details to memorize, or do a report on.

What DO you teach? Teach about the students in the room, and the target culture.