Some more important tips for first time flyers:

Takeoff: you'll probably feel a weird reclining feeling. This is normal. Once you get off the ground, you'll probably feel like the bottom of the plane has just fallen out from under you, almost like a very slow and graceful roller coaster. This is also normal. Takeoff can be a bit bumpy and awkward. You're (probably) not going to die, so enjoy it.

Landing: when you land, it will probably be bumpy. The rear landing gear will make contact first, and not always at exactly the same moment. Then the nose will touch down. Then some rather severe braking kicks in. The "air" or engines will get REALLY LOUD and you'll slow down REALLY FAST. This is normal. You're (probably) not going to die.

In the air: Drink or don't drink. Up to you. After a couple hundred thousand miles of commercial flights, all I can say is that if you get hung over easily, you might want to skip the booze. Airplane lavatories are not the easiest to use and there might be a line. You also might get stuck in your seat for a long time if there's turbulence or other problems. Keep that in mind if your bladder is tiny.

In the air, part 2: turbulence is normal. I remember once I had a dream about earthquakes and woke up to heavy turbulence over the ocean en route to Australia. That was weird. But no matter how hard it gets, your pilot (probably) knows what they're doing and you're not going to die.

On the ground: Airport security has no sense of humor. Immigration staff have even less. On the other hand, Customs staff often do as long as you aren't trying to smuggle drugs and/or bring in quarantined items. Keep this in mind if you ever have an extra bottle of wine or something. It could save you a few dollars on duties and taxes (but be sure to try to declare everything).