Reducing discomfort may be helpful. Wear loose, comfortable clothes and shoes. Bring a chewy snack (muesli bar or dried fruit) for the ascend and descend phases to help with inner ear pressure. You won't be able to get anything from the flight attendants then as they will be seated and belted too. Keep your nasal passages clear if they are prone to blockage, eg have a jacket handy for day flights, a thick jacket or blanket for night flights.
Arrive early at the airport so that you do not get additional stress before the flight. Do not go through the checkpoints or go to the gate at the last minute. Give yourself plenty of time. If you are travelling alone or travelling with someone who is also unfamiliar with international air travel, it may be worth finding out what you need to do and how much time is required for each step from check-in to boarding.
Bring something to occupy your time on the plane. Books or puzzles are easy, but if you intend to watch a video or listen to audio, get over ear earphones to keep out the aircraft noise.
I personally prefer the rear of the plane because I enjoy looking at the control surfaces of the wing in action, especially during take-offs and landings, but most people prefer to sit nearer the front as it is quieter. So it you have a choice of seats, decide which you would prefer.
Keep your seat belt fastened loosely when the seat belt sign is off (and firmly when it is on) and you would not have to worry about turbulence. They are just potholes in the sky and the plane is designed to handle them just as a car can handle bumpy roads.
If all that is not enough, take a child on the flight. Keeping the child entertained (lots of preparation required before hand) should make you forget your nervousness
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