Tying your dog in place by his collar is also an unsafe move it is just a way for him to get a broken neck.
Larger enclosures are available to fit bigger breeds.
Good timing is correcting or praising your dog as he is thinking about doing a behavior.
When your dog has mastered the first step have him Sit at Heel and give him the command to Stay.
Allow at least fifteen to thirty seconds to elapse between each decreased degree of sound.