That is a great link! I willa dd a few comments.

Have the new cat to the vet as soon as you can. You want to have it tested for feline aids, and feline leukemia. You may not want to keep the kitten / cat if it tests positive for either, so you need to have that done even before YOU become attached! Feline Leukemia is highly contagious and you will have to keept he cats separated for life, if you DO keep it. Feline AIDS is only contagious from a bite, saliva, blood contact. I have one FIV + here and it is not an issue for me. BUt it is best to have the test done and KNOW.

Also have the new one checked for ear mites (easily contagious, can be dealt with), dewormed and checked for fleas. All this before the cats have any contact with each other.

Once you start letting them be around each other, keep a water squirt bottle handy. Use it to break up any fights. Now, you will learn over time that they will tussle as they develop their hierarchy, and that will be ok, where as a real FIGHT will need to be broken up before one gets hurt.

I have had intros over with in 4 days, and I have had them last 4 weeks. Just depends on the personalities.

Keep your expectations practical. You CAN insist they live together in harmony. You can NOT insist they be best buddies. That they will have to decide themselves.