@Traverse, kudos to you for asking these questions! I've been flying internationally for 29 years now, but my first time flying was from the US to Canada when I was 21, and I wondered about
exactly the kind of things you're asking. There was no Internet to ask them on, and I was (foolishly) too embarrassed to ask anyone, because everyone I knew had done this a million times and I felt stupid. So I worried about it until I got through the flight.
Stay hydrated. Yes, use the bathrooms at the airport, and you don't have to guzzle water for reasons already given in this thread (!), but staying normally hydrated (and moving your legs occasionally) is important for your body on a long flight (much less important on a short flight).
This may not be an issue on this trip, but if you're planning a trip where you'll need to change planes, make sure you have enough time between each flight. It can be hard to know when you're not familiar with the airports yet, but that's the kind of thing you can google. Some airports are more time-consuming to get around in (and this is exacerbated when you need to change terminals within the airports). You want to have plenty of time to stand in a new batch of lines for security (which BTW isn't always necessary). If you're booking with a travel agent, they can advise you. If you're booking on Travelocity or the website of an airline, you often have a choice of connecting flights. I personally like to have a little too much time; it gives me some wiggle room if the first plane's take-off time is delayed, and makes the trip much less stressful.
I discovered one thing a few years ago. I couldn't figure out why I was often bumped once I got to the domestic US leg of my regular route between Scandinavia and the US, even taking into consideration that it's a lot more common to get bumped in that part of the world. Then it occurred to me that I never got bumped the times I checked luggage (I used to travel with only a carry-on). I asked someone who worked as a gate agent (the person who handles boarding as you're leaving the airport to board the plane), and he said it's more of a hassle for them to bump travelers with luggage (they have to retrieve the luggage). I don't know if that person was right, but now I always check at least a small bag, just as bump-insurance.
It's nice to know that once you get to the airport, there are employees all over the place who can answer anything you might want or need to know.
Have a good trip!
