An aeroplane ticket is definitely required here! There is a wide selection
of international airlines that fly to Australia. Definitely shop around
as prices can vary considerably. Also, check out the option of a round-the-world
ticket, as often these vary little in price from a direct flight and you
can have a few side trips on the way to and from Australia.
Consider a stop-over if travelling from the USA or Europe. Landing in
a strange country is daunting at the best of times, but when you are suffering
lack of sleep and jet-lag it can be a bit overwhelming! A few days spent
at a half-way point can acclimatise you, let you get some sleep, and also
experience another great country.
Don't forget to sign up for frequent flyers points on the airline.