Anybody got tips, apart from bringing your own sandwiches?
Note that customs tend to be on the lookout for
some agricultural products - different ones in every nation AFAICT - that they
really don't want to be imported, not even if you're going to eat them yourself. A stash of sandwiches might evaporate faster than you can get hungry again ...
Stay hydrated!
Sky-high amen to that. That has gotten rather difficult with the "no liquids" rules nowadays, though ...
If you've got a lot of connecting flights, make sure you know the time zones of each place you'll land in!
I actually once had that problem at a stopover that
wasn't listed on the ticket in the first place (and, of course, was so durn modern as to have no wall clocks whatsoever). Smartphones are your friend (wait for the operator to send a NITZ if you have the time, browse the web if not, steal someone else's if that fails, too. Stealing someone's wrist watch requires prior training, though their owners tend to be slower on the pursuit).
I've never done that long a trip; but it's my impression that standing up and moving once in a while, whether or not by heading to the bathroom, is important anyway, to help prevent potentially dangerous problems in blood vessels in the legs.
If you're at all prone to that problem (I'm not, I'm a natural at impersonating a corpse), YES.
Many small problems, especially of the "food or drink ran out or were taken away" kind (or "TSA opened my luggage lock with power tools" or "I need a sleep mask 'cause they can't be bothered to turn down the lights" or ...), have one common, near-universal, potential solution: cash. Carry enough of it,
outside the check-in luggage.
Have a map of the
actual destination (i.e., the hotel or whatever). Make it include the last common-transport waypoint (i.e., likely airport) and the complete contact info (address, phone), in both your and the local language, if applicable. (Asking for directions by shoving a written note into someone's face works better if
they can read it, too.) Be aware that Google Maps is fallible (as in, no, Google, the place where you put the marker in Chennai was
not our hotel but the Russian embassy).
You
will be separated even from your hand luggage at times (e.g., when
that goes through the x-ray). Ponder what you cannot allow to get stolen, and put that in your
pockets, lockable and/or inside ones. Make sure to be able to recognize your luggage from the opposite end of a large hall. If you travel with company, same applies to them. (Ever wondered why large funny hats are such a popular souvenir?)