Driving on Australian roads is somewhat different this travel guide can give you an idea of what to expect.
Luckily for people coming from Ireland or the UK is that you will be driving on the Left-Hand side in Australia so you should fit right in. But if you are from continental Europe or the US then you will have to adjust to driving on the other side as well as using a right-hand-side drive car.
As with most of the rest of the world, road distances and speed limits are displayed in metric (km/h). Speed Limits around the country can vary from state to state. But a good rule of thumb is 100 km/h on the open road and 50 km/h in built up areas; though obviously keep an eye out for the speed signs.
While the roads all over the country are fairly well maintained you will only find motorways on the approach of the major cities. The Sydney Harbor Bridge, the Sydney Harbor Tunnel, and some of the highways and roads are tollways, so have change ready to go through the tollgates quickly. This toll can be as high as AUS$8 but is different depending on where you are so keep an eye out for the price.
In the cities of Adelaide, Melbourne and Sydney you will find that you are sharing the city streets with trams. In these cases, you will have to remember that trams have the right of way at all times. Special mention has to be made of what is known as the 'Hook Turn' in the Melbourne city center. This occurs because of the city's extensive use of trams, and because you will be sharing the road with them special measures are taken. Basically on certain junctions, drivers turning right sit in the left lane across the junction indicating right until the traffic lights change and then turn right.
Some signs you may see on your travels: NO STANDING/NO PARKING, this basically means no parking except to pick up or let out a passenger. NO STOPPING, fairly obvious though you can stop in case of medical emergency.
When driving in the more remote areas the roads are of good quality but may not have road markings so you should remember that even though there is no line in the middle of the road it is still a two-way thoroughfare so you should continue to drive on the left. There are also some roads that don't have a finished surface and many car rental companies won't let you drive a conventional car on these roads. If you are planning on driving in these areas be sure to get yourself a 4x4.
Most petrol stations are open 24 hours and they are usually self-service. On some longer journeys through the more remote regional areas the service stations can be few and far between, so in these cases it is recommended to top up at any chance.
If you do run out of petrol or break down in the middle of the Outback, do not attempt to walk out of trouble, stay with your car as you have a much better chance of being found. It is generally a good idea to leave your itinerary with someone local like the police with an ETA of your return, etc. Given the size of the country you may well be out of mobile phone coverage often, though you can purchase mobile phone car kit with an external antenna that can increase your range or you could get yourself a satellite phone.
You will also have to deal with slightly different wildlife than you are used to. Dingoes, feral camels and especially Kangaroos can move quite fast and can appear from nowhere on the road so always keep these in mind when driving as they can do quite a lot of damage to your car. These animals can be particularly active at dusk where poor light conditions only makes spotting them that bit harder. If you do hit an animal, you are legally obliged to stop and check to see if the animal in question was a marsupial and if it had any young in its pouch as some of these animals are endangered.