Frankly I don't see too many cats in the wild where I live, so they aren't the most common. Usually it's at someone's house. I try and NOT squee and lunge at them, because I know that my ultimate goal of getting said kitty in my lap for pettins, will be defeated if I do. So I play the chill, relaxed hooman card, usually works. In about half an hour, I has a new fluffy lap warmer, purring away as I pet it.You don't just automatically say" aww come here you little pretty kitty" when you see a kitten? I just can't imagine not living life like that.
But doggos, yeah if they are walking past on a leash, I invariably say, in puppy dog voice. "heyloo puuppy!!" and debate whether the hooman will allow me to squat and ruffle their pooch.