Leading Edge Australia in the Global Economy has a good chapter on protection in Australia - it's available at Dymocks in the city. I got most of my information from my teacher who gives us really good handouts, but Leading Edge had some good material.
Basically you should know about how we've gradually reduced/eliminated most of our protective barriers - we still have some in the car industry though. You should also know about what protection is, and how it prevents free trade between nations - to tie in with that you should know advantages/disadvantages of protection and free trade (for example, disadvantages of protection include misallocation of resources, reduced incentive to innovate, and redistribution of income to name a few)