If you are prone to having your ears plug up because of the pressure, buy Afrin nasal spray and use it about 20 minutes before taking off and again about 20 minutes before landing.
Try to organize your carry-ons, with the things you will need more (kleenex, books, tapes) in outside pockets or easy to reach places. I prefer to put my carry-on bag in the overhead compartment. If it is under the seat in front of you, there is no room for your feet.
If possible, depending on the weather, pack your coat in your suitcase rather than wearing it on the plane. You will be lugging around a big bulky coat. For warmth, dress in layers so you can add or take off easily.
Some planes do not allow you to use portable CD players at ANY TIME during the flight. This always makes me nervous, surely if it bad for one plane, it’s bad for them all, right? But if you have a walkman that plays tapes, bring that instead.
Bring a toothbrush and travel-size toothpaste on the plane with you. About an hour before you land, this will be your best friend.
Any travel shop in an airport should have one of those pillows. Mine is the inflatable kind, and I like it just fine. It’s covered in some sort of fuzzy material, so it’s not like sleeping on plastic.
If you are not sleeping, pay attention to strategic times to use the restroom. Use it during the movie. Use it before they come around with the meal and beverage cart … it blocks your way if it is in the aisle. After they collect the meal trays, everyone needs to use the rest room all at once. After the movie ends, everyone needs to use the rest room all at once.
Whenever possible, I bring things to amuse myself that I can leave on the plane or throw away, like big magazines that I haven’t gotten around to reading yet. Or even a trashy paperback that I have no intentoin of keeping. Then I am not dragging this stuff all over the place during my trip.
The movie has a good chance of being awful, so don’t count on it to keep you entertained.
And everything everyone else said already.