Tear lengths of aluminum foil the length of the couch. Depending on the depth of the couch, you may need two sheets.
Place the aluminum foil strips along the seat of the couch. Fold the edge of the foil over the outer edge of the couch. Although the sound is the primary discouragement for the dog, the reflecting light from aluminum foil is discouraging, as well.
Sit on the couch, on top of the foil. When the dog tries to climb on the couch to be next to you, the foil makes a sound that most dogs dislike.
Tell your dog “Down” or “Off” in a quiet voice when it tries to climb up next to you. If necessary, use your hand to gently push the dog back down to the floor before it climbs up.
Reward your dog for getting down. Give it a treat, a pat and a kind word.
Repeat Steps 3, 4 and 5 until your dog learns to stay off the couch.