What do we learn about or know about the couple through the scene's visual design: the props, the set design or dressing, the decor, the camera angles, the lighting. etc?
Later in the scene, we found out Mr. and Mrs. Smith have been in their room for three days, however, I was able to ascertain that they had been holed up in their room for quite some time based on the camera movement, set design, and props. Right at the top of the opening scene, the camera pans across the room showing lots of used dishes around the room as well as the general messiness of the bedroom.
I could also tell the couple was in the middle of an argument or separated somehow based on their blocking in the frame. Carol Lombarde was in bed, hidden under the sheets, while Robert Montgomery played cards away from the bed. I also noticed a sheet on their couch in the bedroom, which could imply they weren't even sleeping together for the night. This furthers the idea that they are in the middle of some couple argument.