A few pointers, primarily realistic safety concerns, because you'll likely have been told a lot of nasty shit about Austrlaia by now (yes, its all true, but no, its not that big a concern if you're in a city).
GENERAL SAFETY:
A common mistake Americans and Brits (particularly Brits) make is not to wear adequate sun protection. No, seriously. This applies mostly if in Perth and its surrounds, but across the entire country to an extent. Why? Because all your bloody fridges and their CFCs tore a hole in the ozone layer, and that damned hole lies not near the countries responsible but right over Australia, pretty much smack bang atop Perth. More than half an hour in midday sun is a foolish endevour unless you're covered with 40+.
If travelling the Nullabor Plain, do not stop on the highway outside of designated rest stops for any reason. That includes helping others who have "broke down". You will likely be murdered.
If travelling the Stuart Highway, take the warning signs seriously, and don't wander from the road. Theres no crazies looking to slit your throat along this road, but there are a butt-tonne of environmental hazards -- theres a damn fine reason the signs are in a billion languages. The desert mostly claims Koreans nowadays (formerlly Japanese were the #1) but theres no reason why an American couldn't join the list.
On rural roads, watch for Kangaroos at sunrise and sunset. You will not encounter roos in the city unless a zoo leaves a gate open. Actually, google image search that shit because there are some hilariously images of smashed up cars from this where the roo literally gets absorbed into the bonnet and displaces the freaking engine.
Spiders are nasty in Australia. In particular, check your shoes if you're in Sydney as theres an angry spider endemic to that city that TARGETS HUMAN FEET, and when poking around behind a house, say, looking for the barbie, watch out for redbacks (only one gender actually has the eponymous red). Most Aussie snakes will kill you.
At the beach, watch for box jellyfish and sharks. If swimming, stick between the flags, if surfing, just crack open a beer and ask the locals to advise.
In bars, glassings to the face or back of the head are common practice, so best just avoid fights. Meth rage has become somewhat problematic in Perth over the last few years.
TOADS:
If in northern Australia (NT, Qld), cane toads can and should be killed, BUT, the corpses must be disposed of. It is irresponsible to leave a corpse lying around as they can and will kill some poor sod's pet and you'll be a hated dude. Ideally, bag the fecker and freeze it to death then drop it in the garbage.
LANGUAGE:
Aussie English words are essentially British styled with American spelling used only when dealing with computers and IT. There are relatively few variations across the country in accent or lingo, although generally Perth leans more British and Syndey leans more American. Accents are essentially limited to 4. Aussie city (incl. Sydney suburbs), Aussie outback, Queenslander and Syndey harbour-sider. The last one is what you'll typically hear on Aussie TV or upon any alien planets that John Crichton has visited.
If somebody "shouts" you a beer or lunch, it means they've offered to pay. I'm still amazed so many Americans and Canadians don't know this one.
"Football", usually means AFL, sometimes rugby up around Queensland. In Perth it often means soccer due to a large British migrant population and a recent backlash against AFL due to general ire towards the local team, the West Coast Eagles over a certain controversial player.
Scallops are a mystery that varies by state.
CUSTOMS AND QUARRANTINE:
Australia takes this shit seriously, particularly WA/Perth. Please, double, triple, quadruple check any consumable shit you bring into the country. And your wood. If in doubt just bloody ask someone because they'll happily help you. The country contains the world's most pristine farmland and anyone that screws that up will face some serious ire.
Pirate goods, some porn or violent games/movies and certain classes of LASERs are also import contraband but this is rarely enforced, nor do genuine Aussies give a shit (kiddy porn excepting).
BEER/BOOZE:
Fosters is stirctly an export beer. Do not expect to find it unless a bottle shop has imported it. Crown Lager is a conjob catering to bogan ideals of faux prestige but tastes similar (a bit better). VB is rather low quality (although if you get lucky and find a bottle of the rare VB classic thats rather nice). Most Aussies drink Toohey's of some sort or other. Stuff like New, Old, or if your bar has the taps close enough to each other to get them in the one jug, "Middle Ages". Yeah, pitchers are called jugs, do not be afraid to ask the bargirl for one, its OK! A jug is 2 L, a pint is 500 mL a schooner is about 370 mL and a middy about 300 mL is most states, but it can vary. South Australia in particular has it all messed up. Most states stock middies OR schooners not both.
Coopers is the best bottled beer by far because its bottle fermented. Comes from South Australia and because the brewry was offered a few good deals to sell out but chose not to, its become rather iconic around Adelaide. Another good drop is Little Creatures from Fremantle, near Perth.
The Australian company Coolabah INVENTED the goonbag, known by some Americans as "boxed wine" (wtf?). Cheapest drink in the country and the best way to avoid the horrendous alcohol taxes if partying at home on a budget; go the fruity lexia, it makes you sexia. 2L goonbags tend to be poor quality.
As for high quality wine, there are a few locally famous regions, but the best by far comes from around Margaret River.
OTHER RECREATIONALS:
Nimbin.
