By birth. If you are born to an American, then that parent can solicit your citizenship through parentage. You have to be under 18 when your parent solicits your citizenship.
Get a work Visa. You can also get into the U.S. through a work visa, or by finding someone that is willing to hire you and give you work papers. Usually this is easier when you work in a field that is in high demand in the United States, such as the health field.
Get married to a U.S. citizen. It is usually easier and faster if you marry in Australia and then your spouse returns to the U.S. and asks permission from immigration to bring you into the country.
The U.S. Citizen Lottery System. There is an immigration lottery system where you can add your name. A certain number of people from different countries are drawn each year. This is probably the slowest and most uncertain way of acquiring U.S. citizenship as there are many names on the list and only a few are drawn every year.
