My fiance's dog Lola and my cat Nicky will be living together soon. Lola's scared of the kitty, and while they don't need to be best friends, they do need to tolerate living in the same space as one another since neither is going to be finding a new home. I've begun the process of rehabbing their relationship, and I'm bringing you all along for the ride.
As the title implies, the very first step in behavior modification is management. Management is all the stuff we do to prevent a dog from doing things we don't like. In Lola's case, I don't want her fixating on and barking at my cat. There are three reasons management is so important that it's the first thing I'm discussing.
The first, and most important reason, is safety. As much as we don't want to believe that our beloved pups could hurt another animal, the truth is that the vast majority of the time, the dogs in our lives are stronger than the cats. Something as simple as over-zealous play could have fatal consequences. But even when your pets are similar in size, kitties with claws can be mighty nasty... and cat bites are nasty cesspools of germs.
Second, we want to prevent rehearsal. You know that saying, “Practice makes perfect”? Yeah, it's just as true for dogs as it is for humans... and it includes both desirable and undesirable behaviors. You don't want your dog to get better at chasing your cat, and I don't want Lola to develop a habit of barking at my kitty. Worse, by allowing your dog to continually harass your cat (and vice versa, because let's be honest, cats can be big jerks sometimes), you will undo all that hard work you're going to be doing.
Finally, management allows us to keep the dog under threshold. Keeping a dog under threshold keeps him in his rational, thinking mind and prevents him from going off in an overly-emotional, overreacting, irrational state. You can't train a dog who can't learn, so we need to keep him under threshold.
So, how does one effectively manage a dog/cat relationship? Well, as so much in dog training, it depends. It depends on what your dog is doing, how severe it is, how the cat is reacting, and what your living situation is. The bottom line is that until your dog and cat are completely comfortable together, you must either be actively working to improve their relationship, or you must be preventing them from interacting. And don't fool yourself: some dog/cat pairs may require management for their entire lives. (Dear g-d, I hope that's not Lola and Nicky.)
Here are some management ideas. They may not all work for your given situation, and I may not have listed every possible solution, but it should be a good start.
Crates are a time-honored way of keeping dogs out of trouble, and they are definitely one method of management I've been using with Lola. The downside of crates is that while they restrict the dog's movement, they do nothing to stop the cat from coming right up to the bars and taunting the dog. While everyone is safe, this doesn't prevent the dog from practicing some undesirable behaviors or from going over threshold.
Baby gates can be useful... depending on your cat. Since they can be pretty agile, it's often no big deal for kitties to go right over a gate. For that matter, there is no baby gate that my dog Pyg hasn't defeated. Bottom line, I would not depend on baby gates to be the sole form of management.
Better than gates are closed doors. Since our furry friends do not have opposable thumbs, most of the time a nice closed door is the best way to keep dogs and cats apart. Just make those doors are firmly latched!
Leashes can be used, either as a tie down to a heavy piece of furniture, or as an umbilical to a person... but only when you're present. I would honestly not trust a leash alone to protect everyone. Slipped collars, chewed leashes, and stronger-than-expected dogs all leave this as less-than-ideal when it comes to unattended pets.
Hopefully this post has given you some ideas... and if so, I'd love to hear them. There are some truly brilliant minds reading my blog, and we all learn when you share!