Introducing a new pet into a home with pre-existing pets can be tricky, but if you follow certain precautions and guidelines you can do it successfully. First you will need to remember all the things you do when getting a new pet. Pet proof your home as required based upon the type of animal you are getting. Know if your pets are naturally antagonistic to one another and prepare accordingly, even if it means separate spaces, such as with cats and small mammals, rodents, snakes and fish.

Each animal pairing is unique; cats and dogs can get along better than two cats or two dogs, for instance. The main trick is the transition and acclimation period. This should be a gentle process characterized by short communal periods separated by ever shortening segregated periods. Give both animals plenty of love during both periods. Be sure to keep watch for potential fights and act to prevent them before they start. Be careful during pet fights. Getting between fighting animals can be dangerous. Your long term pet may respond to your separation attempts best.

Use tricks to build comfortable familiarity such as removing a played with toy or piece of cloth from each animal's private space and placing it into the other pet's area. This gives each animal a chance to get used to the other's scent, and thus their presence. Their reaction to the item can also give you valuable clues as to how the animals may respond to one another when placed together.