Having animals are great for kids. However, since your baby girl is still very young it may not be a good idea to get a little kitten. I recommend that you get an "older" cat - maybe a year old or so. Getting two may be even better, the cats will entertain themselves if you are gone all day. Also, some shelters will not adopt kittens out to households with very young children.
Precautions - of course you need to supervise your girl and cat especially in the early toddler stage when your girl will try to grab them. For the cat, make sure it has a place up high, that is out of reach of the little one, as a safe place to relax. If you get a high kitty-condo, make sure that it is anchored to the floor or wall and can't fall over onto cat or baby, like you would do a dresser or cabinet. Also, the litterbox should be accessible to the cat and not baby. A baby gate into the room would work, just keep a little space underneath or make sure that the cats can climb over.
Introduction - I don't think special intros are needed to your girl. She'll be delighted to see a cat hanging around. If you have other animals, then you may need to do special introductions. The shelter will help you with that if you ask them.
Other things we learned: When we got our cats, we exclusively played around a scrathing post so every time the cats grabbed the toy with the claws, they felt the post. Today they only use scratching posts (and carpet) for the claws, not our furniture. We also give the kitties a "pedicure" - clipping their claws and it is quick and easy to do. We got them used to it by grabbing the cats once a day, put them on their back and hold their front paws and pretend to clip them.
Last, make sure you teach your girl to use kitty toys to play with them, not the bare hands. One of our cats cannot distinguish between a hand and a toy and uses claws everytime she plays. Since your girl is so young you need to make sure that cat toys with strings don't have strings that are too long. That's all I can think about now - good luck with adopting...
N.
Sparta, NJ