In the far North, the remote Kimberley is a huge chunk of wilderness with astounding scenery. The Pilbara is a (hot) mining region, very lightly populated, with however various natural attractions worth the stop. The coast of the Gascoyne in the middle of the State offers various wonders: the Ningaloo Reef is far to be as famous as the Great Barrier Reef, but it easily equals or surpasses it in beauty, and Shark Bay is a UNESCO world heritage site. The Western coast (Mid West) has various surfing beaches. The closer to Perth, the more temperate the weather and hospitable the landscape. Regions around Perth (Great Southern, Heartlands, Peel, Perth (region) and South West) are laid-back agricultural, with some fine wineries in the South and large forests.
A few hundred kilometers inland, the inner area of the state (technically divided between the Kimberley, Pilbara, Mid-West and Goldfields regions) is a huge remote barren desert with little to no population. This area encompasses fully several of the Australian deserts: the Great Sandy Desert, the Little Sandy Desert, the Gibson Desert, as well as parts of the Great Victoria Desert and the Tanami Desert. It is extremely challenging to access, and requires a lot of preparation.
These are some of the major towns and cities in Western Australia.
Western Australia is a huge monster sized state encompassing various climatic zones (from the moonsonal and tropical north, to the temperate and mediterranean South, and the desert and barren inland). Apart of the Southwestern coast, the majority of the land is extremely old, eroded, flat, arid and infertile. The population centers are extremely isolated from one another, and from the other populated zones of Australia. This and the tough environment may account for a more independant spirit than the Eastern counterparts of the state, and there have been several referendums in the past where it was close to actually become a separate country (in 1933, the population voted in majority for secession, though no action was taken).
The vastitude of the state is certainly not to be underestimated when planning your trip: the state is actually larger than any of the European or African countries (even larger than Denmark with Greenland), and twice the size of Alaska. Visiting anything else than Perth will probably require some long driving.
English is the only language you will need, in case you meet someone in the more remote parts of the state...
Whatever the way you decide to get into WA, remember that there are very strict quarantine rules if you are coming from abroad, or from other states. You can not bring fresh food (including fruits), and even several kinds of processed or frozen products might be forbidden. Check beforehand on the Western Australian Quarantine and Inspection Service site to avoid bad surprises. Rules are enforced, including for rail or road travellers. The best option is to buy your food once in WA.
When the daylight saving time is not in place (October-March), there is a 1.5h time difference with South Australia and the Northern Territory. From October to March, there is a 30 min with the NT and 1.5h with SA.
Perth International Airport (PER) is the only airport in Western Australia with regular international flights. The vast majority of interstate flights also land in Perth. However there are a small number of interstate flights to Kalgoorlie and Broome.
Considering the huge distances, driving into Western Australia from anywhere else is an experience by itself.
There are only two sealed roads into Western Australia: in the south, the Eyre Highway is the most direct route from Adelaide to Perth. In the north, the Victoria Highway connects the Kimberley region with the Northern Territory up to Darwin. Both imply extremely long drives. Perth-Adelaide is at least 3 days of driving with stops only to sleep. Darwin-Perth is at least a week.
Unless you have a private plane, be ready to drive a lot to get from point A to point B. There are only a limited number of sealed roads (any map of the state will probably show you all of them), if you plan to leave them to get to more remote areas you will need to consider renting a 4WD. Contact the company to which you rent the vehicle to check the policy concerning driving on unsealed tracks, as you might have to get their authorization. Usually driving a rented conventional (non-4WD) vehicle on an unsealed track is forbidden.
Sealed highways and byways
These roads are not what most people would call a "highway" or even a "road". They are unsealed and should definitively not be taken lightly, especially if you have no experience in driving off sealed roads in the Australian desert. Be extremely cautious if you decide to attempt these tracks, as they are adventures on their own. Petrol supply is scarce, water is rare and accommodation is close to non-existent. These roads should only be used with thorough research beforehand, and a 4WD is very strongly recommended. On some more remote tracks, it could be weeks until anyone finds you or your body if you break down.
If WA does not quench your thirst of (harsh) wilderness, it is unlikely that anywhere else in the world will.
Besides driving, which can be an experience for some (being on the only sealed road for hundreds of kilometers, without crossing anyone, might be either disturbing or enjoyable to most of Western Europe drivers), WA offers nice surfing on its beaches (around Geraldton for instance).
There are wonderful diving spots in WA. The Ningaloo Reef is probably THE place to dive, but there are other areas scattered along the Indian Ocean coast (even around Perth and Rottnest Island).
Although you can expect the usual outback delicacies in roadhouses (sandwiches, steaks...), as well as some reasonnable options in Perth and the larger towns, including nice seafood, WA is probably not the top destination for a gourmet. A trip in WA will probably require some amount of self-catering, would you decide to get away from Perth a bit.
The fairly recent Western Australian wine business may not produce the large quantities of the wineries of the Southeast regions of Australia, but there are a few bustling vineyards that may attract the visitor, especially around Margaret River. All the major vineyards are located in the South of Perth.
In the outback, bring a lot of water with you.
The vastness of Western Australia requires travellers to be particularly careful when going into remote areas (which constitute the majority of the state anyway).
Leaving Western Australia will probably be as hard (or as simple) as getting in, unless you decide to pay a visit to the Principality of Hutt River. By some obscure legal technicality, this small farm near Geraldton successfully declared its independence from Western Australia in the 70s. You can even get a passport, buy rare stamps and coins and if you are lucky you can even meet the Royal Family.