I'd buy currency now, I usually wander around where the big banks are, look at their exchange rates, also check the official exchange rate online to get an idea of what you should be paying.

Also, sign up for webjet, virgin, qantas emails, I also get emails from 2 major travel agencies. There are a few other online flight places that you can get cheap flights through.

Once you work out which airline, maybe get a year's membership with their "club", it is useful if your flight is delayed at anytime, because you can sit in their lounge and not be sitting around the airport. With Qantas you get priority baggage check-in too (which is handy, your bags come out first!)