Dogs and cats are generally considered fierce enemies, which is why the phrase "fighting like cats and dogs" was coined. However, dogs and cats can learn to live with one another. Though they're very different creatures with unique needs and wants, dogs and cats that are trained properly and put in the right environment can learn to get along and even enjoy each other's company.
Focus on training the dog. Cats are very independent, so rarely do they follow commands. It’s better instead to ensure your dog understands and obeys command like “sit,” “stay” and “leave it alone.” These three basic commands should be taught before the dog and cat are introduced.
Maintain a firm grip on both the dog and cat when you first introduce them to each other. Alternatively, put them both in crates and place the crates close to each other. It will give them a sense of security and make them less likely to misbehave. Choose to do this away from food bowls and other areas the animals may feel protective toward, and do not introduce them during feeding time. If one begins to exhibit aggressive or fearful behavior, separate them and try reintroducing them again at a later time.
Supervise the dog and cat whenever they're together. They should not be allowed to mingle freely until you are certain that they're secure around one another.
Shower the dog with attention anytime it is in the vicinity of the cat. This way he will learn that being around the cat is a good thing, which will reduce any nervousness or malicious feelings he has.
Place the cat’s food in a hard-to-reach area so that the dog won’t try to eat it. Make sure the cat can still reach it. There is no need to worry about about the dog’s food because cats generally dislike dog food. If you ever catch the cat nibbling at it, do your best to discourage it.
Establish a safe zone for both the cat and dog. They should each have their own private space where they can relax and feel free.
Avoid punishing one as a means to rescue the other. If a problem occurs, separate the two into their safe zones. If you punish the cat for taking a swipe at the dog, for instance, then the cat will associate punishment with the dog's presence.
Promote coexistence. After the dog and cat have been living together for a least a month, start forcing them to spend more time together. Hold the cat on your lap while the dog is in the room. Give them both treats at the same time.
Be patient. The process will not happen overnight. It could take weeks or months before the dog and cat finally settle into a routine of coexistence that they're both comfortable with.