First of all, you can't really learn how to teach a cat not to hiss or meow at friends but to strangers instead.
Hissing at threatening strangers is pretty much hardwired into a cat's psychology.
You simply have to train him who he can trust and reward him for not hissing at friends and family.
Much will depend on the cat's background.
If a cat started life as a feral kitten (which happens in cities as often as in rural areas), he may have a harder time warming up to people.
To earn a cat's trust, particularly with a skittish cat, it's important to approach him without sudden movements and loud noises.
Each time you'll be able to approach him a little closer.
You may be able to speed things along by offering a cat treat.
Eventually, a cat will let you touch him, but probably only briefly.
You have to build up trust step by step.
Some cats have more outgoing personalities and will walk right up to a stranger for a pat on the head, but most need to be convinced.
If a previously friendly cat suddenly starts hissing when you approach, don't feel weird becaue he may be injured or sick.
Evaluate the cat's condition, and if necessary, call the vet.
Many problems, like urinary infections, can be easily cleared up with a course of antibiotics.
Injuries may need veterinary treatment, too.
If you're trying to get your cat to warm up to visitors, tell your visitors to ignore the cat when they first arrive.
(If they have a cat, they probably already know this.
) Otherwise, the cat will feel threatened and will have to overcome that apprehension when choosing to approach a visitor.
Unless there is something that is particularly threatening about a visitor, your cat will make at least some progress toward the visitor before he or she leaves.
It takes time and commitment, but cats can be taught to be relaxed and friendly around visitors.