Without knowing what you are going to say, I am a bit limited in offering advice. However, you could easily use rhetorical questions to lead into the speech as a whole or any of its parts. For example, you could begin with "What is an Australian?" You could then follow up with a series of different possible answers, ultimately ending with your thesis (perhaps something like "An Australian is not just someone who holds Australian citizenship, but someone who feels a strong connection to the country and its people and who embraces the values that form the core of Australian identity" or whatever other criteria you choose).
Similarly, you could introduce a section of your speech with a rhetorical question, such as "How do people's relationships with the landscapes they inhabit influence their behavior and their sense of self?"
However you choose to incoprporate rhetorical questions, remember that their purpose is to inspire thought and engage the audience, so use them in writing situations that are well-suited to those goals.