Share a song, TV show, movie or game that your partner hasn't heard, seen or played before!
And have them pick something to show you in return.
For example, You have binge watched the entire series of Black Mirror but your partner hasn't seen a episode.
Pick an episode that you think they will enjoy and soon they'll be hooked
Actual experience by this writer, who's boyfriend got her hooked onto Black Mirror after one episode
And they can, in return, get you into the Buffy the Vampire Slayer TV show
Again, based on writer's experience
You'll not only discover more about each other interests, but you might become a fan!