Be direct with each other
When Elizabeth heard cheating rumors about her husband, she turned to him in "Passage" (Season 1, Episode 7) to get the straight story knowing he wouldn't lie to her.
Elizabeth: Are you having an affair? I heard it, but I don't believe it. But I need to hear it from you... Oh, my God.
Elizabeth: Well, you're going to have to be a lot more convincing immediately.
Henry: Have you completely lost your mind?
Elizabeth: Okay. That's better.