When it comes to dogs and cats getting along the amazing thing is that sometimes they actually do. They seem to be natural enemies the way cats and mice are. Their communication styles are so different as to be almost exactly opposite.
There is no logical reason for them to get along, yet, by some miracle they often do and pet owners can encourage this with the right actions.
It starts with the premise that the cat is always right. No matter what the cat is doing to the dog, consider it justified. Unfair as it may seem, dogs should not be allowed to retaliate.
In a fight between a dog and a cat the cat is rarely ever the winner, they often end up hospitalized or worse. When forced to choose a side in a fight, error on the side of the cat. Cats can’t do much harm to most dogs. (The exception to this is dogs with protruding eyes.)
Praise your dog when he is being gentle and tolerant of your cat and guide interactions with clear directions; a soft “easy, gentle”, works wonders.
If your cat seems too rough with your dog or especially aggressive, seek professional help. Many dog trainers, like me, work with cats also.