Making international calls requires using a given country's country code, which is entered before the rest of the number. Australia's country code is +61. On most cell phones, there is an option to include a "+" symbol by holding down the 0 button for longer than normal.
Sometimes, when calling from a land-line phone, you must dial 011 before dialing the country code instead of "+." Therefore, the sequence would be 011 61, followed by the phone number. Australian phone numbers never begin with 0, and all area codes in Australia have a single digit, which is dialed before the remaining 8 digits. All cellphone numbers in Australia begin with a 4 in place of the area code.