Get an old rug with a rubber backing and a pair of utility scissors. Welcome mats also will work, if the bottom is rubber.
Cut circular pieces from the rubber-backed rug or welcome mat. The pieces should be slightly larger than the bottom of the couch legs.
Apply a nickel-size amount of super glue to the carpet side of one circle.
Lift the couch and press the glued side of the circle onto the bottom of one couch leg. Hold the circle firmly against the leg for 30 seconds.
Gently lower the couch and repeat the process for each remaining leg. The rubber backing will prevent your couch from scooting around on your hardwood floors and causing damage.