There's one word to take out of Octanes post; that is CONFIDENCE. I did my OSB at Tamworth in 06 and I didn't project as much confidence as I could have (the board president can be pretty intimadating!) and my marks showed that, but I got here in the end and I'm living the dream here at RMC.
You have to go into the OSB as if your already in and they are asking you to stay, but also know your sh!t. Know, and be able to clearly explain how something flies, exact platform specs and wpn systems with ranges (including ones coming into service) the REALISTIC trg timeline. The little 1%ers, all in detail, but also be ready to say that you don't know, DO NOT bull****, that goes for the DI and the OSB.
Good luck and ENJOY Tamworth, it's an awesome two weeks with some really switched people.
Now to go and run around the bush for a few weeks in nice dry and sunny QLD... hang on....