The link that Bitwise used is correct on the origin of the inward V sign.
This is the little rhyme I learned as a child
“The wee boat sails out to sea (spoon scooping soup away) then comes back to me.” (To one’s mouth)
Not a thumbs down! Now those are offensive.
Re “honou” - stupid Gaudere’s Law.
The webpage seems to be quite old fashioned even when it is technically correct. Sure, you should probably call someone Mr Miss or Mrs on meeting them, but I don’t know anyone who actually does this outside of formal functions.
Taxis, I always get in the front, sometimes I talk sometimes I don’t. If it’s 5:00am (the time I’m normally get a taxi) then I don’t say boo.
Limos are another matter, you normally get a limo so you CAN sit in the back and sip champaign or whatever.
Thumbs up means just the same here as it does anywhere else. If it was used in another way (and I’ve never seen it) then, as you say, it would be obvious as a seperate gesture to the “thumbs up”
I think they were more then a bit nervous and none too happy either.
It’s funny, your location says Sydney but I find that hard to believe. I give people the two fingers all the time. It’s pretty much the same as the middle finger, but it can be changed a bit to mean, well, lick my c*nt, you asshole.
I always thought we Aussies invented the thumbs up, as the perfect side dish to go with a “g’day mate”.
What’s with the Yank spelling of arse ?
I thought you were an Aussie 
Cecil Adams on Why do we nod our heads for “yes” and shake them for “no”?
Cecil Adams in What’s the origin of “the finger”? doesn’t discuss the obscene V sign but does debunk a similar legend about the digitus infamis.
Maybe she affects an American accent in her day job as a dominatrix?
Anyway, I’d second Atticus as far as the booze is concerned. Bring wine if the hosts are sophisticates, beer if working class, either if they’re anything in between. But no matter what the quality of Aussie wine is like, it isn’t like bringing sand to the desert because sand doesn’t taste very nice.
You remember than book and movie about some EDS employees getting kidnap just before the revolution that toppled the Shah? In that story, it was stated that using the Yank’s thumb-out gesture to hitchhike would get you into a fight instead of a ride. (Make a fist, palm inward, and extend the thumb in the direction you’re headed to get a ride in the US.) They said you wave your arms to flag a ride in Iran.
Not really.
That site is talking about the middle finger only gesture, and adding in some obvious nonsense about “pluck yew” becoming “f*ck you”.
The page does scoff at the practice of cutting off the middle fingers of captured bowmen but offers nothing beyond their own assertion for this. I’ll continue to accept the longbow theory as the origin of the two finger salute for now.
The 2 fingered gesture is a different thing entirely, it has a less defined meaning and is generally considered less rude than the single finger. I’ve never seen any serious cite disputing it’s origin with English longbowmen.
TAXIS
I always ride in the front seat if I’m alone. Australians are aware this is an unusual custom internationally, so we take delight in exercising it as our birthright.
It is acceptable to ride in either the front or the back, and it is also acceptable to be either chatty or quiet towards the driver regardless of where you are sitting. I once asked a cabbie about the seating arrangements, and his answer: “I prefer it if people sit in the front. I feel safer as I can see their hands and I can fight back if they try to attack or rob me. If they are sitting behind me they can grab my neck and I’m at their mercy.” Although many taxis now have shields around the driver, I still remember what that guy said, and it’s an added reason for me to sit in the front - especially as I’m physically large and I catch cabs late at night. This is also why I usually do engage the driver in conversation - just to put him more at ease. It’s a dangerous job, that one.
One other thing with taxis (though this custom is diminishing in favour of a more US approach) is that the fare is often simply rounded rather than an actual tip being worked out. This means sometimes the driver will, in effect, tip you. If the fare is $19, you’ll give the driver $20 with “that’s alright”. If the fare is $21, the driver might say “twenty’ll do mate”.
GESTURES
Thumbs up is pretty safe. Australians use it 90% of the time in the same way everybody else does. It can be used in a semi-obscene way to mean “piss off” or “go away”. This will be very obvious. Usually the thumb is tilted to one side a bit in a symbolic “go that way”.
As mentioned, two fingers is only rude with the palm inward. It is the same as the British usage. This used to be the only rude gesture, but the US style one finger salute has taken over in the last ten or twenty years. Most young Australians these days would have no idea about the two finger one.
That site has much that is bullshit, but one thing that really rings true is their advice not to use Australianisms. Stick to international English.
G’Day, and thanks for the replies, mates!
Only kidding.
I originally didn’t think that site was full of shit, b/c the American one seemed OK to me. Nice to know to avoid it in the future. How can they get away with saying things like “I’m stuffed” means “I’m pregnant” when it is completely untrue? Don’t they have fact-checkers? Oh well.
Lucky for me I will be in Auckland with the wife and another couple, so somebody will have to sit in front of the taxis.
One more question about the soup: is it really considered rude if you ladle it towards you? Will people look at me strangely? I doubt I’m going to remember that. Not that they’ll assume I’m anything other than American with my knife-fork-reverse-hands thing. 
I’ve noticed that travelling as a man in the Middle East, SE Asia & Latin America (although I have more limited experience with taxis in the latter two; in most of SE Asia you’re actually sitting on the rear of a motorbike) that sitting in the front seat is pretty standard. Sitting in the back would be seen as pretentious. Rules change for women because of gender issues in culture (a woman sitting up front with a male stranger could be scandalous in parts of the ME) and/or to keep her out of groping distance. In the case of a longer distance louage in Tunisia the car isn’t going anywhere until full so you may as well grab the front seat if there first.
I think it’s pretty cool that Australia (I’ve never been) has a relaxed enough society that people will sit in the front; also a safe enough society, as in most American cities of any size there’s plexiglass bullet shielding between the front and back seats to keep the driver alive.
I think that website was suggesting not to feel like you need to bring wine into the country from abroad because Australia produces plenty. That’s a seperate issue than bringing a bottle over for dinner. May be the first thing the site got right…
I doubt that anyone will even notice which way you ladle your soup. 
Women can’t wear pants?
In Canada while in high-school, when I was dating a young lady from Liverpool, England, I was invited by her parents to a family dinner. When she tok a goodly helping of food on her plate, I made the innocent comment: “Wow, you’re really going to get stuffed.”
Much blushing and harrumphing ensued from her parents and sister. Over the next few days, each one of them quietly tok me aside and explained that to them “get stuffed” meant “get pregnant” at best, and “get fucked” at worst.
I don’t have a clue what the usage is elsewhere, but for that one particular family, it was quite clear.
And why I can’t spell tok properly is beyond me. Tok is not a conventional spelling as far as I know.