25 hours? Where are you flying through?
My advice is, don’t sleep the night before, or sleep as little as possible…
If you are getting into Sydney in the morning, I feel for you.. You are going to have a rough day.
If you’re getting in say around 7pm, I will go as far to say you wont even have any jetlag – I didnt have any when I got back from Barca..
So on the plane – the reason not to sleep the night before of course is to wear yourself out so you sleep almost the whole way here 
(it CAN be done )
I sometimes take puzzles and ipod on the plane.. I’m sure youll also have your laptop?
Take a deck of cards with you.. and make friends with one of the ‘hot’ flight attendants – believe me, youll thank me for suggesting this.. they look after you the whole flight. talk to you if you get bored and pretty much give you whatever you want
There is a good couple of hours of chat there..
Make sure you get up and walk around by the way, or you will have pregnant lady feet..
Books – you should find an Aussie dictionary and brush up on your Aussie before you get here.. Actually thats a hint for anyone flying in from somewhere else.. I can guarantee you will have to ask more than one person to repeat themselves coz you have NFI what they just said. Youll also have a bit of a laugh too
If all else fails, there is always the mile high club 