The best thing we did? We made a huge deal about how big of a treat it is to fly. I made a deal with my kids weeks ahead of the flight--I said I wouldn't make them sleep and they could have as much screen time as they want. They couldn't believe their luck!
NO regrets. Both kids watched shows on the seat-back screen/iPad and then conked out for 7-8 hours. When we landed after about 16 hours on the plane, my 3-year-old exclaimed, "That wasn't long at all."
We booked a red-eye flight out of the country (Newark to HK). The flight left at 1:00 AM. It was a great idea. The kids napped during the 3.5 hours it took to get to the airport and then adrenaline powered them through hours past bedtime. Then they conked out not too long into the flight because they were legitimately exhausted.
Don't overpack carry-ons. We only kind of did this, but I think it's good advice. I hate having to corral all sorts of crap in our teeny airplane seats and I equally hate being bogged down by multiple/heavy bags in airports. I know many people recommend bringing wrapped presents for each hour of the flight to distract kids, etc. but I think ultimately, my kids were old enough to be satisfied with screens (iPad, in-flight TV, Kindle) and maybe a workbook or two. (That said, when we flew with a 1- and 4-year-old, it was nice to have some toys--like Play-Doh--for Lucy, who was too young to be interested in screens).
I think next time, I'll pack everyone's carry-on even lighter. I've learned I don't really need much for myself--my Kindle, my phone with a charging cable, moisturizer and chapstick, a small snack (like trail mix or a granola bar), wallet/passport, pen and a notepad, and an oversized scarf. Since it wasn't a work trip, I didn't actually need my laptop/charger on hand--and those add a lot of unnecessary weight.
I've alluded to this a number of times, but if you can afford an iPad, get one. (You can get an old one from Craigslist for $150--my kids use a hand-me-down first generation iPad with a cracked screen.) It will be your best friend. Load it up with new games and shows and your kid will be entertained for hours. I'm generally mindful of limiting my kids' screen time (which is really the key to making it such a treat) but dude, as far as I'm concerned, transcontinental flights are an exception.
That said, here's the bottom line: Last time we flew to Asia, Anna was four and Lucy was 1. Lucy screamed for 7 hours of the 15-hour flight. Our mistakes? Giving her Benedryl at the advice of our pediatrician and, well, simply deciding to fly across the world with a kid who just learned how to walk. I'm mostly kidding about the latter because ultimately, we survived even the nightmarish screaming, BUT it's just inevitable that trying to restrain a newly-mobile, very active child for 15 hours just won't go well. This time around was downright EASY and I think that's simply because my kids are older (and can be bribed with an iPad). I believe we need to arm ourselves with humility and low expectations, hoping for the best but being okay if things don't go smoothly. Because...
Bottom, bottom line: we had a great time with our relatives in the Philippines and it was absolutely worth saving up for tickets and traveling the 34 hours total each way. At the end of the day, even if the flights/traveling are horrible, it's just 34 hours of your life.
Things that helped on the trip:
spill-proof water bottles (emptied out for security and then refilled at the airport/on the plane)
sturdy kid backpack with adjustable straps--anyone in the family could carry it comfortably
a super lightweight carry-on bag (this is a newer version of the bag I've used every time I've traveled in the last several years and I love it. It can be carried as a tote or a backpack, which is genius)
an oversized jersey scarf that can work as a blanket
a Kindle loaded with library books for all the readers in the family
an iPad with new games/shows
lightweight kid headphones (these have a volume limiter. And we found even child-sized airplane headphones slipped off the kids' heads, so it was definitely worth bringing our own. Lucy used these and Anna used my pair)
endless bags of airplane peanuts
(Sorry for the bad quality iPhone photos--they're all I took!)