Well, first of all, with a pup, you need to decide on the word. It will be confusing to her if at this point you use STOP and NO interchangeably. I use the word EH! I can bark it sharp and quick and it definitely gets their attention. Then I use that attention to do something even more fun -- direct them to a ball or chewey or toy.
Pretty soon, a simple EH! will stop them from whatever they are doing. Down the line I will use ENOUGH! for getting a dog to stop a behavior that is maybe not wrong in general, but is annoying all the same, like barking when someone comes to the door. ENOUGH! tells the dog that I have it covered and he needs to stop right now.
They can learn various words for the same command, but starting out, you need to be consistent, and you need to follow through. Like, if your dog is chewing on the leg of the table, EH! dog looks at you, and you squeak a toy and have him chase it. If he then drops it and goes back to the table leg. EH! and move him away from the table and play tug with something of a different texture. But you have to follow through. If the dog is barking and you want her to stop barking and you just say EH! and the dog continues to bark or whine, so you just throw up your hands and go off to read on the porch -- that won't work. A better approach would be to teach the dog what to do, rather than what not to do. Dog is barking, Eh! dog stops and looks at you, "Good Quiet, good girl" Use that word Quiet a lot, and when she is quiet, Good Quiet and treat. Pretty soon, the dog is barking, Eh, Quiet! And the dog then knows that he must be quiet.
Dog is jumping up and being an overall nutcase. Teach the dog to SETTLE or GO TO YOUR PLACE. Tell the dog what to do, instead of reacting to what the dog is doing. That way you can give a new direction to the dog, instead of just shoving a toy in its mouth. GSD puppies are intelligent which makes them curious and will get them into trouble. Be sure to give yourself breaks where the puppy is in a safe place -- crate or kennel, so that you have the energy to play with your puppy and teach it what you want it to do. Because if you leave her to figure out stuff to do, it might not be to your liking, and worse yet, it can become a habit that you will have to break, or self-rewarding, like counter-surfing or digging. It can also be very dangerous.
Good luck with your puppy.
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