Rabbits aren't tameable in real life. You can cage them but they still won't act any different than a wild rabbit and will try to escape if you let them.
Dolphins are lured by dropped items that are inside nearby water blocks, knocking them around and chasing them. If the dolphin can not find a path to a dropped.
To tame a stray cat, you will need either Raw Cod or Raw Salmon. It normally takes anywhere from 1-10 fish for the cat to become tamed (depending on RNG).
Technically, you don't actually tame cows in Minecraft like you would tame a wolf or parrot. You can, however, lead them, breed them and even milk them.