How do you address a woman in an informal and friendly manner? I know mate but this one is mostly for blokes, isn't it? All I can think of is baby or doll, but I've got the sensation that these are a bit too familiar/predatory.
If the woman is a stranger, you should not use any such term at all, as many (if not most) women would think that offensive, and overly familiar.
If the woman is a friend, you would of course already know her name, and that is how you would address her.
It really does not work both ways between men and women. The brash waitress can get away with saying to the male customer "All right, sweetie, what can I get you?", but it would not be equally friendly for the man to open the conversation by saying to the waitress "Sweetie, would you bring me some coffee?"
if you know her name, then address her by her name (use Miss or Mrs. Surname if she has not given you permission to address her by her first name - wait until she indicates that you may use her first name)
if you don't know her name, such as when speaking to a waitress, address her by Miss, or madam