Before you bring home a cat or kitten, make sure your dog knows two basic commands: "Leave it" and "Stay." You're going to be saying those words a lot in the first couple weeks, so the time to practice making sure your dog knows them is before you bring home your cat or kitten. Here's how to teach your dog these useful commands:

• Stay. Start with the "Sit," with the dog at your side, holding the leash in a straight line up from his head with all the slack out. Flash an open palm in front of your dog's nose and then say, "Stay." Step out in front of your dog so that you can block his forward motion. If he moves, snap the leash to correct him, flash your hand, and repeat the "Stay" command. If he stays, return to your position alongside him after a second or two, tell him "Okay," and praise him. From there, it's a matter of building up time and distances in slow increments. If you're working at the end of the 6-foot leash and your dog is staying reliably, tug on the leash a little without making a sound. If he moves, go back and correct him with the leash, repeat the command sequence, and try again. If he resists the tug, return to your position alongside him and release him with an "Okay" and praise.
• Leave It. With your dog in a Sit-Stay and your hand in a fist, flat surface up, offer your dog a biscuit with the other. As she reaches for it, say "Leave It" and bop her under the chin, enough to close her jaw but not lift her off her feet. Offer the biscuit again, repeating the "Leave It" command, and if she hesitates or turns away, praise her. Few dogs need this demonstrated more than twice.

Never tolerate aggressive behavior from your dog. Keep a leash on him until everyone's settled and use the "Stay" and "Leave It" commands to keep him under control.

Although some cats and dogs maintain an armed truce, at best, others become the best of companions. These things take time, however, so be patient.