set them up in their own room with food water and litter..  Take your cues
from the resident pets.. when they seem interested and not aggressive to the
newcomers, open the door.  where there is a dog, you'll want to keep the dog
on a leash to control him.  You might also want to do face to face intros
through a baby gate or screen door, so you can judge how everyone is going
to react when they can meet one on one.  Go slowly.  Explain to all the pets
the situation.. yes.. in english.. and often.. also praise the resident cat
when she shows no aggression.. make the new cats a good thing.. by giving
extra attention and treats when they are around.  The more aggression anyone
shows, the longer the introductions should be.

Good luck

Keep them apart for as long as possible...
they will have to get used to the "foreign" smells.

Then...only let them mingle briefly and do not try to introduce them
by pushing them together.

I know that when I once brought a new cat into my house where I already had
a cat...the two of them never became good friends...but after about 6 months
or so ...they could at least tolerate each other!

When I move into a new house I take all my cats in their
respective carriers, open them up so that they all
enter the house at the same time.   No cat has an
advantage.  
--------------------------------------------
"Finally a member of the Jackson family finds
another young boy to victimize."
-------------------------Jimmy Fallon on SNL
                        referring to Justin
                        Timberlake

To send me e-mail exorcise NO Spam from
my e-mail address.

I shifted 5 times with my last cat and it got easier each time.  It got to
the stage where the cat was happy so long as I was around and she didn't
really seem to care where she lived but the first shift was the most
difficult one and took about 4-5 days to adjust.

Make sure you have one of their favourite things available, e.g. a blanket
they always sleep on.  My cat liked to hide in a small spot until she felt
comfortable with the place.  The cosier the better.  On her first shift it
was usually hiding under the bed covers so if your cat goes there when
they're nervous try to get the bed made up quickly.

Try and find a place where they can hide, e.g. a cupboard or under the
bedcovers and put their favourite things there.  Give them time to adjust
and don't push them to adjust too quickly.  Make sure their food and litter
box is close by.

If your cat is an indoor/outdoor cat don't let them go outside too soon,
they should have settled into the house first.  When they do go outside make
sure it is under supervision and that they come back indoors by themselves.
Cats have been known to disappear for days on end if they are not happy with
shifting.