How can I keep my dog off the couch?

One thing you can try is putting empty cardboard boxes or a long sheet of aluminum foil on the couch; this startles your dog when he tries to jump up on the couch and he will self-correct by not getting on the couch anymore.

Provide them with another comfortable alternative. Get them a bed or put a pillow on the floor next to the couch. They really just want to be close to you! Not staying there? Hide treats in the bed or sit with them next to the bed the first time. Maybe you make them do tricks in their bed. You want them to feel like its a safe place -- long term, only give them potty treats after coming in from outside when they are back in their bed! Make them go there first and foremost.

I agree with the aluminum foil! it has helped mine in the past and after a while i remove it and they just know :)

Try offering an alternative to the couch such as a dog bed and tell the dog in a stern voice "no". You can offer a treat or toys on the dog bed or area where you would like the dog to go to.

Dogs respond well to rewards, so I would suggest being consistent in telling them no and moving them to the floor. Then, afterwards, rewarding them with a treat for staying on the floor. It'll take time and consistency, but it would be a lasting solution. In the meantime, you could consider purchasing a deterrent spray from your local pet store!