Here are some useful guidelines for introducing a new cat or kitten into a home:

• Set up a comfortable "safe room or area" for New Cat and one for your current feline if he/she is feeling stressed. Put her toys, and bed or other sleeping mat there.
• Expect a great deal of "hissy-spitty" behavior through the closed door from both cats. This is natural and normal; they are just starting to explore their "pecking order."
• Scent is very important for cats. Let each of them smell the other indirectly, by rubbing a towel on one and letting the other smell it. They will soon accept the scent as a normal part of the house.
• Once or twice, switch roles. Put New Cat in the normal living quarters, and let your resident cat sniff out the new cat's Safe Room/Zone.
• Let the two cats sniff each other through a baby-gate or through a barely-opened door. Gauge the rate at which they seem to be acclimating to each other.
• When you think they're ready, let them mingle under your supervision. Ignore hissing and growling, but you may have to intervene if a physical battle breaks out. Again, take this step slowly, depending on how quickly they get along. If they do seem to tolerate each other, even begrudgingly, praise both of them profusely.
• Make their first activities together enjoyable ones so they will learn to associate pleasure with the presence of the other cat. Feeding (with their own separate dishes), playing, and petting. Keep up with the praise.
• If things start going badly, separate them again, and then start where you left off. If one cat seems to consistently be the aggressor, give her some "time out," then try again a little bit later.
• This process can take anywhere from a a few days to a month - just be patient and you'll be rewarded with 2 very happy cats !