How do I address strangers in Australia?

Other respondents have covered this well (which is a benefit of me putting off replying to A2A’s!)

I’ll just add some metacommentary. People of Quora who get me in their feed because they like me or something: do read the other responses.

• The egalitarian ideal of Australia is that we address each other as mate, because we are not Class-Obsessed Poms [British]. But that’s an ideal, and it has its limits. It’s not really appropriate for someone substantially older than you. Mateship was also was never really a female friendly thing, though that has eroded somewhat.
• There is also something of a class factor to mate. Australians are in denial about there being class in Australia (because, again, We Are Not Poms); but all the grumbling about bogans is nothing if not classist.
• Mate is fine for males younger than you, including teens and kids.
• Darl and love were addressed to women in the bad old days; hence Sarah Boon asking noone keep using them. I have been addressed with darl and love myself by older women, mostly in service industry contexts; but it is decidedly antiquated.
• Zero-address is safe, as others have said, precisely because we’re uncomfortable with more formal alternatives to mate (such as sir—which we wince at even in service industry contexts), and we have a lack of female alternatives. (Mate towards women is limited, probably odd to most people, and certainly only addressed to women you know, not strangers.)
• Ma’am has actually gotten me adverse reactions. I do use it, but as an ironic thing.