Generally, people quiet down after dinner is served, but there is still the noise of people and flight attendants moving about the cabin, not to mention the occasional enraged baby.
Be sure to include all of your charging needs in your carry-on, including converters that work in your destination and anywhere you may stop in between.
Convert your money into pounds/Euros before your trip, at your American bank, usually for no or a very small charge. Be sure to have at least a little cash with you when you arrive.
You do not want to miss a single minute of exploration time trying to track down tooth paste in some random city.
Though it'll make your bag feel a bit cramped, make sure you have enough underwear, socks, and a *full* change of clothes to get you through an entire day and a half in your destination.