Access the website of the Electronic System for Travel Authorization (ESTA) at least three days before your departure for the United States. Only Australian passport holders or nationals from other countries that participate in the Visa Waiver Program are authorized to use ESTA to get clearance to travel to the U.S.
Complete the online application. You need to have your valid passport at hand while completing the form. When finished, press "submit."
Print or note on paper the application number that appears on the screen. Following the application, you will be prompted to make an immediate payment for the service. As of 2011, the fee is $14. Only credit or debit cards are accepted. If an immediate payment cannot be made, you can save the application and return to it later to make the payment. Your application will not be approved until you make the payment, however. The ESTA approval will be electronically linked with your passport number.