For countries that do require a visa, remember they are non-negotiable, so don’t think you can just wing-it when you turn up at your given destination if you accidentally forgot to get your Visa sorted out.
You should also know that some countries issue specific visas for specific visitors like tourists or students or business visitors, etc.; and some visas are valid for just a few days and some for a few months. It is also important to confirm if you visa is for single entry or allows you to leave and re-enter your chosen country multiple times.
The Department of Foreign Affairs and Trade (dfat.gov.au) has lots of useful and up-to-date advice for travellers who need to obtain visas, but remember the department doesn’t issue visas for overseas travel. For that you need to contact the embassies of the countries you plan to visit directly for the most up-to-date information on their specific visa requirements.
A hot tip to remember is that sometimes it can take a while to be issued with a visa so make sure you plan in advance and apply for your visa well-before your departure date.
Also keep in mind the Australian government is unable to intervene if an Aussie is refused a visa or denied entry to another country so make sure you are thoroughly organised and have a valid visa before you leave the country. If you are refused entry, you will need to shoulder any additional travel costs.