Okay, I've flown 10 trans-pacific flights within last 4 months (5 roundtrips), and this is what I found works for me.
First of all, and most important for me, invest in a good set of noise-cancelling headphones. I have the Sennheiser (sp?), and it is simply wonderful. Make sure you have a spare set of batteries, or put in a fresh set of batteries for the pack. On one of the flights, my batteries ran out and I had to do without the noise-cancelling part. It drove me nuts, and the difference is night and day.
I also try not to sleep the night before, so when I get on the plane, all I do is sleep. In-flight movies are hard to watch, and even on flights like Cathay Pacific, where you get those personal LCD screens, you get bored quick.
Don't drink alcohol or too much liquid of any kind. It really sucks having to wait in long lines to use the lavatories, especially going in right after someone who dropped a stinker. I can usually do without using the toilet even during the long flights.
Wear comfortable clothing, especially pants and shoes that are not constricting! When seated in upright position for a long time, your lower extremities tend to swell up, causing extreme discomfort. Try to avoid wearing tight jeans or shoes. China Airlines always provides a pair of slippers for you to use during the long flights, and I love them for it. And their blankets are some of the warmest. It does get very cold during some time, so bring a sweat shirt/fleece jacket you can easily shed and put back on. Even with the blanket, it gets really cold.
Use those travel neck pillows and eye-shade thingies if you have them. Cathay Pacific provides eye-shades and toothbrush, but I don't remember any other airlines that do. Little things like these can make a big difference.
I usually put on my Sennheiser headphones right when I get on the plane, tune to one of the music stations on low-volume, and sleep throughout the flights. I usually listen to the airline-provided music stations, because I want to be able to listen to the announcements. If you're flying an Indian airline, then there will be an Indian music station available. When I flew China Airline, there was a Chinese music station, as well as American music station. When I flew Cathay Pacific, there was Chinese, Japanese, Korean, Malay, and Thai music stations. And Philipine Airline had Filipino music... you get the idea.
Some of the best airlines are Cathay Pacific and China Airlines (not to be confused with Air China), with excellent cabin features, friendly staff, good food, and smoking-hot flight attendants who provide excellent service. They will fuss over you, if you can manage to say some basic things in their native languages. Did I mention they are smoking hot?
Some of the best deals are Eva Airways, if you book Eva deluxe class. You get business class-like legroom and amenities, without the business class price. It's usually only couple hundred dollars more than the economy.
Some of the worst is Philippine Airlines and Northwest. Philippine Airlines' crew was very unprofessional, and even rude (not to me, but to many others around me). The cabin was so cold, I thought I was gonna freeze to death. Many others complained of the icy condition, but the crew couldn't care less. Northwest crew is comprised of unionized, jaded old ladies (at least everytime I flew), who provided some of the worst service. I was told because they are unionized, they don't give the extra effort their Asian counterparts always provide. I'm not being too harsh, as I hear same thing from many other people who flew their trans-pacific routes.
If all fails, you can always whip it out and....