Compliment each other
Just because they've been together for years doesn't mean they stop flattering each other. "Well, there's a sight that never gets old. You know, if men knew how sexy they looked fixing stuff, they'd never stop," Elizabeth said at the sight of Henry repairing gutters in a light snow in "Spartan Figures" (Season 1, Episode 19).
Henry returned the favor to Elizabeth when she was nervous about singing in front of a crowd on "The Show Must Go On" (Season 2, Episode 1):
Elizabeth: I can sing right? I mean a little. I'm not awful. Right?
Henry: Are you kidding me? Those Beach Boys songs you sing in the shower, you kill it every time. I mean the good kind of kill.