Which technique is best used to ensure that students will focus on the most
important topics during a discussion?

To ensure that students will focus on the most important topics you have to discreetly draw their attention to it. Add pictures and imagery or interesting facts. If you hook them at the beginning with an activity that is fun for everyone like a Kahoot! They are more likely to focus on learning anything that they see, so all you have to do is bring the important questions in the games and such. Also stray away from anything that will confuse them, such as mentioning multiple topics at once. I hope this helped