Australia is incredibly protective of its national borders and population, but it has one of the simplest visa systems in the world. People from most western/European countries can apply for a travel visa online at The Australian Electronic Travel Authority (ETA) website (http://www.eta.immi.gov.au) before they enter the country and that basically gives you the authority to be in Australia on holidays for up to three months. Everything happens online within about 30 seconds and that's pretty much all you need to do.
As always, there are plenty of exceptions, if you have a criminal record, have been refused entry to Australia before, been deported, or you come from Columbia and have white powder in your moustache, you're going to have a bit more trouble getting in. If you're not from the list of eligible countries, you can apply for an ETA at an Australian Visa Office and some travel agents and airlines.
Want to know more? Got a Question? Discuss it in our Australian Travel Forums