First thing you need to do is get a visa. Unless you hsve strong ties with Oz you will only be eligible for a yearlong working holiday visa. I got mine through STA travel (they charge a fee for processing, but you can do it yourself).
You have 1 year from the start of the visa to enter australia, and then a year in Australia after that.
You need to make sure you have enough money to suuport yourself in the short term, and also provide evidence of funds to get home (or a return ticket).
I would recommend starting in a major city down south (melbourne or adelaide) that way you can aclimatise yourself, both to the weather and the "lifestyle". All major cities will have backpackers hostels, and they will be packed full of people in the same situation as you, so no need to worry!.
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Like a sinner before the gates of Heaven...
