That is a very interesting question because in a certain way australian propaganda set a standard of a recruiting rhetoric that was used later in Europe (during WWII and further). Australia as one of the British dominions was automatically involved in the war since the questions of Australian foreign policy were under the authority of the British Empire.
According to the famous expression of Australian Prime Minister Joseph Kook, when the Empire is at war, so also is Australia. So for the government it was very important to develop an effective scheme of a propaganda to make the citizens support governmental position. What is a war propaganda and how it works you can read in this paper. And precisely about the propaganda in World War I - here and here.
There were two primary goals war propaganda in Australia:
Three basic motifs of a propaganda were used. The first one was a motif of a shame. Hundreds of war posters said something like
It is nice in the surf but what about the man in the trenches
Are you content to hide yourself behind the blood of men and the sorrow of women?
Take your share of your troubles going and never go back on your mate
The second motif was patriotic. Where the object of patriotic attitude was not Australia, but the British Empire:
The Empire needs you!
Australia has promised 50,000 more men, will you help us keep that promise?
And the third motif was promising of adventures:
Free trip to Europe! Full of adventure and interest, forming the greatest event of their lives [...]
Frankly, I was amazed to see Australian war posters. Some of them are just examples of beautiful copywriting, professional design and marketing. No kidding! Chem them out here.