Replace your couch's legs with mid-century style legs. These legs are often made of wood and are tapered. Some are slanted outward.
Reupholster the couch with a solid color or choose a solid color slipcover. Choose common mid-century modern colors such as bright red, orange, yellow or more muted but still mid-century modern such as grey or beige.
Tuft the couch to give it a more mid-century modern appeal. Button tufting helps the couch have a more modern and geometric look. You can button tuft the couch yourself or hire a professional upholsterer.
Remove throw pillows from your couch. Mid-century modern couches were sleek and rarely were styled with many pillows.