Of all of the large breed dogs, the German Shepherd's intelligence makes it easy to train. But like any other dog, it needs to have a reason to do certain things and treats are always an excellent reason in their eyes.
When you come home from work and your German Shepherd is lying on the couch looking like hubby waiting for the game to begin, (only without the six pack), then you know its time to teach it to stay off the couch. There are devices that are manufactured for that reason but they are not, in my eyes, good training tools. There is a mat that rings a loud bell when doggie jumps on the couch, and literally scares the poor thing off. Another mat is made of plastic and looks like the mat that you have in offices under chairs.
There are little spikes that are supposed to make the German Shepherd feel uncomfortable when it tries to lie down. In my opinion, spikes may be uncomfortable but they can also hurt the soft skin of the underbelly. You can also use sprays, on the couch, that are supposed to deter the German Shepherd from using the couch. However, when you spray the couch enough times with these sprays the smell will deter your use of the couch also.
German Shepherd dogs are intelligent, so why not train yours to stay off the couch using a natural method? Natural training takes time and patience. Your dog may think it owns the couch, and it may also think that it's a lap dog and want to sit on your lap on the couch. When the dog is on the couch then use a command such as “down,” and show the dog where down is by pointing. When it gets down, then a treat and applause is in order.
The treat should be something that it would not ordinarily get and this is good training. Continue to say down and give a treat until the dog knows that the couch is off-limits. With a German Shepherd this will not take long. However, as it begins to learn, decrease the treats. The dog will then stay off the couch in anticipation of getting a treat and once in a while it should not be disappointed.
Never scold or hit the dog for being on the couch. The dog does not understand why it is being abused and will soon become frightened of you. A frightened dog is not a very good companion.