
All my life I have traveled Economy Class (only once did I get lucky and got an upgrade to Business Class). In my opinion, flights of up to 7 hours in Economy are tolerable, but more than that and the all the fidgeting and frustration starts getting to you.
Having lived in Australia for 3 years, I dreaded the 14 hour flights to and from Dubai (30 hours if you include transfers and waiting); that's when I realized how seemingly trivial things could drastically change the quality of your flight.
MSN just published an article listing some of these small yet significant tips, of which I think these are the most important:
Be comfortable: Wear loose, warm, long, comfortable clothes. Stick to flat shoes, preferably ones you can wear socks with. Being warm and comfortable in your clothes will change the nature of your flight. (It's such a basic point, I don't understand why so many people choose to make a fashion statement on board at the expense of being comfortable. Perhaps they should stop making movies that make people believe they will find "the one" mid air.)
Bring lip-balm: Even if you have never-cracking lips, on a long-haul flight darling, they
will crack! I carry lip-balm everyday, everywhere I go, and always have it on a flight. Once I forgot it and my lips chapped like tree bark. (Yes, ouch). I kept going to the bathroom and putting that disgusting hand-lotion they keep in there on my lips. Didn't work, and yuck, never again.