For the food part I did pretty much what MuleNag suggested-create a negative association with the cat's food. We had a problem with Sophia scarfing the cat's food-not good because a) I don't know who is eating what and b) the cat food is too rich in protein for the dogs. Allowing cats on the counter is not an option, so I brought Sophia over to the cat food bowl, put her nose in it and said "NO" loudly. This created enough of a negative association that she leaves it alone.
That pretty much goes along the same lines as rubbing a dogs nose in its poop if it goes on the floor. You aren't supposed to creat negative associations to prevent something, so you're supposed to use positive reinforcement. Please don't give improper advice on message boards where people might actually use it. My cats know the difference between the counter that their food is on, and the kitchen counter, and they do not get on the kitchen counter.