In no particular order:
1. Choose your airline wisely. Everyone knows that United is rubbish, so don't do that to yourself.
V Australia is excellent. Delta is excellent. Lufthansa is also good. Sometimes the cheapest option on Expedia is not the best. As my wise mother likes to remind my cheap-arse self, you get what you pay for.
2. Be ready to walk out the door the night before you leave. Sometimes I still fail on this one. But when I'm really on top of things, I like to have absolutely everything packed and ready to go the night before. I find that if I have time to relax before heading out the door, then I'm more likely to have my "Aha! I forgot to pack my [...one or more of power adaptors/hairbrush/phone charger/pajamas]" moment before leaving the house.
3. Be able to carry your checked luggage up a flight of stairs. Because you're going to have to.
4. Become a Master of Organisation. This isthe most important one. You have to be organised every step of the way. At the planning stage: make sure tickets and accommodation are booked before all the good spots are taken, travel visas are ready on time, and you have either sufficient money in the proper currency or a plan for getting that money (along with a back-up for when your card turns out not to work internationally). At the packing stage: ideally, pack your suitcase so that the first things you're going to need are the most accessible. Travel documents - all of them, including booking confirmations and directions for how to get from the airport to the hotel - should be filed in your carry-on. At the boarding stage: put everything you are sure to want during the flight in an easily accessible location. Reading material, music, extra layers for when the A/C comes on, Purell so you don't catch Ebola, and a pen for filling out your landing card. And during the flight: organise your time. Fourteen hours is a long bloody time to sit in one spot, so make a plan for what you're going to do with yourself to avoid being bored out of your everloving mind.
5. Check in before all the aisle seats are gone. Because obviously. You are guaranteed at least one armrest to yourself and all the toilet runs you want.
6. Dress in layers. The plane will be freezing when you board, then cycle between sweltering hot and frigidly cold in 40-minute intervals for the remainder of the flight. The blankets they provide are purely decorative.
7. Bring emergency rations. And be smart about it. Decide in advance when you are likely to start feeling peckish, and choose your snacks appropriately. For me it is usually about eight hours into the long flight (halfway between the miserable excuse for dinner and the miserable excuse for breakfast), and then again during whichever layover(s) follow. Fresh produce, meat products, and (sometimes) nuts/seeds cannot cross international borders, so they will have to be eaten before you pass through customs. If you're travelling to the US, you pass through customs immediately upon arrival, regardless of where your final destination is. Remember that yogurt counts as a liquid at security, dry salty things are good for motion sickness, and the other passengers are liable to flay you if you pull out something smelly on the plane.
8. Set your expectations appropriately. There will be screaming babies. There will be queues at check-in, security, and customs. The plane food is going to suck. The movie selection is also going to suck. You are going to have to fight for your armrest. Your suitcase will probably be among the last of several hundred to come out at baggage claim. If it comes out at all. Accept these things as the facts of life. They are the fundamental truths of travelling. Do that, and then when something good happens - you arrive at your departure gate to find that they are offering free coffee and snacks, for instance - it will feel like a gift from God.
9. Relax, man. As soon as you board that plane, you have the next 10-14 hours to sit back and ponder the whichness of the why as people bring you hot food and cold drinks. There's no need to worry about making it to the departure gate on time, or keeping track of your passport, or responding to work emails, or whether you remembered to pack underwear. Honestly, if it wasn't for the snoring man beside you, the crying baby across the aisle, the bad food, the lack of space for your legs, and the funky airplane smell, flying would practically be like chilling at a 5-star resort.
10. Keep travelling. Just be patient. Eventually, you will find yourself on an 11-hour flight from Seoul to Munich with two empty seats beside you; take-off and landing will be smooth, there will be a basement with eight separate washrooms and never more than one or two people in the queue, and dinner will come with a vanilla custard brownie for dessert.