I fly quite a lot to Asia, though never to Australia.
It's really about selecting a decent seat (whatever that means to you) and then getting into a state of mind about travel.
The most important aspect is getting sleep where you can.
On eastbound-flights (EU to Asia or US to EU) try to get as much sleep as possible. Sometimes that means having a meal (and maybe a drink or two) at the airport prior to departure and then trying to get to sleep as soon as the seatbelt signs go off.
Remember to tell the flight attendants that you do not want to be disturbed during the meals/drinks service. Also remember to keep a fastened seatbelt visible while you sleep, in case the seatbelt sign goes on.
On some flights, if you book seats right at the back, you may be able to find a three- or four-seat row that is completely empty. Baggsie it as early as possible and then enjoy sleeping horizontal in economy without the price of the more expensive cabins.
There is plenty of time to fill out any forms or landing cards in the hour or two prior to landing, so don't worry about doing that as soon as you get the cards.
On the Westbound flight, I tend to try and stay awake, as the landing is usually early evening local time. I might doze after a meal and a drink, or if working, then I'll work throughout the flight.
I take a laptop or tablet with my own music and movies and plug that into the in-seat power (if the airline has power in the seat it's a big bonus). The screen is much better than the seat-back units on most airlines. Also, you have your own choice. I use the time to catch up on TV series I missed (I have a computer-based PVR) that can save to a disk.
I also use noise-cancelling headphones to mitigate the noises from young children. (I have flown as a parent with young children, and want to give them all the support I can, but I also want to be able to doze, or read without constantly tutting at young children who are suffering from over-pressure in their ears).
Finally, I try to get assigned to a bulkhead seat, partly because I am tall and want the legroom, but also, once airborne, you can get out a bag and store it within easy reach - and the most important reason - you can get out to go to the loo without disturbing your fellow passengers (or being disturbed by them).
Often you have to pay for that, but I have found it is most definitely worth it.
Then there is all the standard advice about keeping hydrated, drinking lots of water, and exercising to avoid risk of deep-vein thrombosis.
But mostly, it is lovely to just sit there and have people bring you food and drink, with no phone calls or emails to get worked up about...
I go into a kind of limbo - spending time reading; doing puzzles, listening to music, or working