Take the kityy to the vets for vaccinations and a virus test. Then
he'll be safe to be introduced to your cats.

Your local animal rescue organization should be able to lend you a
trap.

Anna sounds like he's a feral...if he's that scared and you've been feeding
him for awhile..I'd say just pick him up and put him in a kennel If he'll
let you. any other questions? E-mail me direct through my website

http://lauraspetrescue.tripod.com

The trapping problem is difficult.  I used a steel trap (not sure what
it's technically called) to capture the adult feral I adopted.  If
you're genuinely concerned that you'll inadvertently catch one of the
neighborhood cats (and simulataneously scare away any cats who
happened to be watching), then you could monitor the trap and do some
selective sniping with a water pistol to keep the unwanted ones at
bay.

Whether the stray will get along with your indoor cats is anyone's
guess.   My feral is very submissive, and she gets along great with
roommates' dogs and cats.  She has no interest in defending her
territory/food/whatever.  She observes but does not approach other
dogs/cats.

I was able to get a voucher from the local humane society and have my
feral friend spayed and vaccinated for free.   Don't know if you have
a program like that in your area.  My cat's been very healthy for the
past 4 years (the vet guessed she was 1 when I trapped her), although
she came into my life with a major flea problem and some infected
lesions.

IMPORTANT NOTE: If a cat has grown up feral (and isn't just a "stray,"
accustomed to human contact), then don't expect him/her to be a good
pet in the classic sense.  He/she will likely never permit any kind of
physical contact, as is the case with my cat.   Thus, you'll have to
"re-trap" the cat for every trip to the vet, which can be quite
exhausting.  But, if you keep your expectations low and regard this
cat as a wild animal who happens to eat and sleep in your home, then
the two of you will get along fine.  I've been able to scratch my cat
under the chin once or twice (but only for a few seconds) in four
years, and she no longer runs for cover whenever she sees me, so we
are making slow progress.  A roommate once tried to wash and groom my
cat and acclimate her to human affection, but the effort was utterly
unsuccessful.  While no stitches were required, several boxes of
bandages were employed, and the experience was frustrating for both
parties.

P.S.  On the plug side, my feral needed no introduction to a litter
box, and she's perfectly quiet (only meows after getting painful shots
at the vet's office), and I never have to worry about being kneaded
awake with sharpened claws in the mornings!

Hi Anna,

I have adopted several strays over the years and am in the process of
bringing in yet another as we speak and what I feel is the best way to go
about it is to let the little guy come to you.  It is my opinion that if you
trap him, you could very well instill a fear and distrust in him about you
that he will not out grow. I feel its always best to let the kitties come to
you on the kitties terms. Good luck.

Hi! Anna,
 I often find strays myself and take them in and feed them until I can find
them a good home. The cat you have needs to be tested for feline lukemia and
aids before you even let him get near your other two. I would carry him to
your vet and tell them about your plans for him and that you have two other
inside cats at home. They will give him all the necessary shots, test and
care he needs.
 If he's wild,  I would suggest  to continue feeing him and setting outside
with him during that time.The more time you spend with him the less afraid he
will be.
  I have a male stray cat outside now.... that was wild at first but now he
seems to be really tamed. I spend alot of time outside with him when I can.
I'm trying to find him a home because I already have three myself. They are
all very precious things. Good luck with him and if I can help just e-mail me
at Lennie88 at aol dot com
Lennie