Throwing in my 2c worth...
- Don't load up on beer. Getting to the bathroom on a big plane is a royal PITA unless you're sitting at the back.
- Don't wear giant belt buckles or other metal objects that will set off the metal detector. Wear sneakers without metal inserts if you can.
- Don't take anything sharp with you because they'll take it away from you and you don't get it back.
- Don't try to take a giant pile of stuff on the plane with you because there's precious little space to put it. You'd like to avoid having to put it below the seat in front of you because it obstructs your legroom.
- Know what to do at the airport. The routine is: check in, get boarding pass, check luggage (if necessary), go through security, head for the gate as noted on your boarding pass. Be at the gate at the time indicated on the boarding pass (the boarding time, not the departure time). They'll probably board by rows, starting at the back of the plane. If you don't want to get on until the last minute, that's fine, but you won't find any space to stow your carry-on bag.
- There's a small air vent above the seat, usually operated by turning. For some reason I like to have a moderate stream of air coming down while flying - it makes it seem less "stuffy". There's a light switch there as well if you want to use it. There will be a small button on the side of the armrest on one side which will allow you to recline your seat a bit.
- You probably will have the choice of a window, middle, or aisle seat. The middle is the least comfortable. I like the aisle because I have a bit of space next to me.
- If you've never flown, you'll be a bit startled at the noise and vibration during takeoff. But now that you know to expect that, don't let it bother you.
- Chances are overwhelmingly good that you'll have a very smooth flight. Once you're off the ground you won't even know you're flying. Take a music-generating device and some headphones and you can zone out the whole trip except for a short period at the start and just before landing when they will tell you to quit using your "personal electronic devices", keep your seat fully forward, and lock your tray table in the upright position.
Your flight will go very well, no worries!