In my experience, the students were asked to respond to a series of questions that could be used for debate purposes; meaning the students had to form an opinion of a topic and state their reasons for their opinion.
They also had to read some selected books to respond to as well, but that could have just been for my city (I'm not sure if that particular portion of the speech contest would be used county wide).
I found that using
http://iteslj.org/questions/ helped when trying come up with questions for the students to talk about.
Also you can find small news articles and such for the students to respond to (also with worksheets) for a more in depth, current event conversation.
http://www.breakingnewsenglish.com/ Practice fluency and overall expression of their opinions. They are looking for students who can express themselves clearly and fluently, so pronouncation practice may help as well.