This is a nice exercise that comes in very handy if you drop a steak or pass a dead skunk. It tells your dog that whatever he’s looking at is definitely not his. We teach it by not letting him get to the attraction!
First, step on your leash, or let it drag. Offer a treat to your dog, and as he reaches for it, cue him to “take it.” Now, hold a treat in each hand, keeping one hand behind your back. Open the other hand, and when your dog reaches for the treat, say, “Leave it” and close your hand over the treat. Do this again and again and again. Patience is the key here—it sometimes takes 20 times before your dog stops pawing or nudging for the treat and looking at you in confusion. When he backs away and looks at you questioningly (“Why are you showing me the food if you don’t intend to give it to me?”), praise him, close that hand, and offer him the treat in the other hand, saying, “Take it.” Don’t give him the leave it treat, or he may just stare at your hand until it opens up.
The next step is entertaining but does take coordination! Tie your dog’s leash to something immovable, and show him that you have a treat. Slowly put the treat down beside you and say, “Leave it.” When your dog goes for it, step in his way, and say, “Leave it” at the same time. If he’s like most dogs, he’ll try to go around you. You—being very coordinated—will keep your body between him and the food. If you need to, step on the treat to avoid having him get it. Within seconds, most dogs get discouraged, back up, and sit. When he looks at you, mark and give him a treat from your hand. Don’t let him get the other one. Pretend it’s a dead skunk or some moldy old hamburger—surely you wouldn’t want him to have those things, would you?