A visa is required in the form of an Electronic Travel Authority (ETA) to travel to Australia from the USA, Canada, or the UK. If you are traveling from another country, please consult the Australian Embassy in your country. 

You must obtain an Electronic Travel Authority (ETA) in advance of your departure online. It costs $20. This will be electronically linked to your passport and is required upon entry into Australia.  Apply for it here. Note that you must download the Australia ETA app on your phone to complete the elecontric visa application. A separate application for each traveler needs to be completed. A step-by-step process can be 

Make several photocopies of your passport. Leave a copy at home with your family and carry a copy with you at all times when you are overseas for identification purposes, money changing, etc. If you should lose your passport, having a copy will speed up the process of replacing it.