My dog stands up when I walk away
- face the dog and walk backward. If the dog jumps up - take a step forward towards the dog, stretch your hands to the sides as if you were to block the dog, ask to sit again;
- ask your dog to sit in a corner - the dog has less distraction from the back;
- ask the dog to sit on an elevated place - a box, a bench, etc.;
- deliver the treat to your dog when you return to them and place it under the chin to prevent the dog from leaving the position before the praise.
Not able to keep the position long enough
Try to focus on giving cookies DURING the Stay and actually not at the Release or any time afterward. One of the goals for this exercise is that we can make the Stay the best part of this, and not the Release. Another good thing to remember is that a Stay is simply a prolonged body position. So if the dog is consistently breaking the Stay after a short amount of time, then stop saying Stay and just work on an "extended Sit" instead. This way there is less pressure to 'perform' for a command. Inbetween rewards, praise your dog. Dogs will often stand up or break the position if they aren't receiving any feedback for their performance. So they may try and do other behaviors in an attempt to receive validation from you.
Dog lies down after a few seconds
Be sure to practice on a non-slippery surface. Dogs slide very easily on wood, tile, laminate, etc. Practice on a carpet or rug at first and keep the Sit/Stay SHORT! (10 seconds at most) at first to really encourage that Sit. If they start to slide down, immediately step in and say "Oops!! Sit" and lure the dog back up to a Sit. Do not treat right away. Praise instead and after a couple of seconds, then treat. Don't practice on their bed as this will likely only encourage them to lay down.
Most common mistakes
Moving too fast
Start with just a few seconds and slowly increase the duration. In the beginning, don't move or talk; face your dog. When the dog is successful and can stay in the position for a few seconds, take a step back and return to your dog. Later, increase the duration and the distance between you and the pet.
Not releasing the dog at the end
It is important to give a release cue at the end of the exercise that signifies to the dog that they are allowed to leave the position. If you don't teach your dog the meaning of the release cue, it will be unclear how long the dog has to hold the position. As soon as you look away, walk away or disengage, the dog might think they are allowed to leave the position.