I do 1:1s a bit weird apparently. I usually have to warn the people reporting to me about it.
Basically, it's their time to talk about whatever they want. I encourage them to come with an agenda and specific things to talk about.
Usually the first few times they'll start talking about their tasks, and I stop them to say, "I'm happy to hear about these, if it's what you want to talk about. So is it what you want to talk about?"
It takes a few of these for them to realize that I'm serious.