For "leave it" have him sit or lay down. Put something that he can't have a foot away. When he goes for it, say "LEAVE IT." firmly and push his snout away. When you get to the point where he hesitates, give him a treat. Keep doing this. We've gotten to the point where I can drop a chip or piece of chicken in front of him and say leave it and he ignores it. Practice leave it randomly throughout the day with 3-5 minutes sessions with treats also. Good luck!