I have a 15 week golden retriever/irish setter mix. He is so smart. He is already house trained. I have already trained him to sit, shake, lay down, come & we are still training to him to stay. There are a couple of things that I need help on. We take walks a lot. When is a good age to train him how to walk properly? How do you train him to do this. When we are walking he is all over the place. I've almost step on him several times. He also pulls. Also how do you train a dog to drop a toy? He's great on fetching & then bringing the toy back to me, but he won't drop.