I have been on over 90 plane trips and 9 international trips( from Australia), my top tips would be.
Get to the airport 1.5 hours before the flight, better to be warily than late
At screening take any laptops or IPads out and place them into a separate tub, also chuck any thing in your pockets into your bag before you enter the queue, take off any belts and other metal items. (Watches don't usually set it off)
Check for free wifi after you have walked and sat down at your gate, the airport normally has free wifi.
Once on the plane find your seat and make SURE it is your seat, if you plan to sleep put everything into the over head lockers if you are able to(you will need to be one of the first on the plane to do this)
Don't get comfy until the seatbelt sign is off, if you are going to use a laptop don't bother with it until the plane is in flight.
Planes are quite noisy, don't expect it to be easy to sleep. Especially if it is your first flight.
Don't bring MIFI or other personal wifi, they aren't allowed!
Watch out for ear pressure, read up about ways to stop this and be prepared.
Enjoy the flight and don't rush to get off the plane, everyone usually stands up once the plane lands and then has to waits till the door opens, just wait it is so much easier.