The first thing about a flight to Europe--I've flown only to London, Paris and Frankfurt from California--is that it's boring, just be prepared for the long length of time and after the dinner, try to sleep. Out of a 9.5 to 10.5 hr. flight. I usually manage to sleep 4-6 hrs. The rest of the time I'm probably just dozing, your eyes are closed but still you hear everything around you. But, with 6 hrs or so I am basically fresh once I land, which is usually from 930 to 1100 AM local time. I try to look for a flight that lands before noon local time.
Usually flying over there from Calif. means that the wind is on your back, which means arrival in London, Paris, or Frankfurt will be earlier than scheduled. If they say the scheduled arrival in Frankfurt or London is at 10 AM, I can figure that I'll get there by 9:40. I am used to a 10 hr. flight; if it goes beyond 10 and half hrs., I start to get impatient and anxious.
I don't take any sleep aids or anything like that, usually have some red wine at dinner so I'll be able to doze off faster afterwards. The more I sleep during the flight, the more fit I'll be upon landing. When I went in my 20s, (the three times over there), I never had put up with something which is now usually the case once I land--jet lag. Figure on three days for that to pass.
Depending on the movie selection, I watch one or skip it entirely. They say don't drink caffeine during the flight...I don't think it matters either way; the coffee is sometimes so weak that it has no adverse effect on me. But try to drink water from time to time, if you can't sleep. AND, I reserve ahead for the first couple of nights once I land and have no desire to waste time or energy looking for a place.