Long plane trips generally involve sitting for extended periods in an extremely dry, noisy, air-conditioned environments in close quarters with lots of people and if you are travelling from Australia, they usually also involve having to adjust to different time zones.
As someone who travels extensively, I have a strategy that involves drinking plenty of water, declining offers of alcohol, limiting food intake, and strategically using dark chocolate-coated coffee beans (I prefer not to drink coffee) to stay awake so that I can adjust to a new time zone. I also use melatonin (2 mg) or valerian to help me sleep when I arrive at the new location.
Your plane trip can be made more comfortable by taking your own earplugs, neck pillow and comfortable eye mask that provides total blackout and indicates to flight attendants you do not want to be disturbed. I also take a pashimina shawl to supplement the airline blankets as planes can get cold at 30,000ft and you may be seated under a draft. During the flight, take your shoes off, stretch your feet and legs often and take every opportunity to walk around the plane, making sure to wash your hands regularly to help avoid picking up unwanted germs.
While seated there are a number of yoga exercises and meditation practices you can do to pass the time. Having your own MP3 player will allow you to be in control of your entertainment as not every airline offers entertainment on demand. To provide mental simulation and inspiration, I like to download the latest TED talks (see www.ted.com) as well as having tracks that provide relaxing ambient soundscapes that assist in blocking out background noise. Having your own personal noise cancelling headphones is also a bonus.