Traveling back and fourth to the middle east and Central America I have come up with a number of things that I keep stashed in my carry-on since I cant rely on luggage showing up or I may need to “make do” while transitting. This stuff is not uber glamorous or high speed but is nice to have on long layovers and the delays.
-Itinerary packet
Detailed information on paper for your travel with notes from previous trips to same area (i.e. pick up companies, travel agencies, etc). Before your trip google some info from each layover and destination (i.e. rental car companies, hotels, trains, etc)
-Maps
At a minimum a map of the area around the hotel, port, airport, etc etc for each stop along the way so that when you hit the ground in each place you can find your way. Even if it is just an 8.5x11 printout that you keep in your itinerary packet.
-Compact sleeping bag
I have used a snugpak merlin 3 and a jungle bag for this. I have no problem throwing my bag out on the floor in a “secure” terminal and secure my bag to me and catch some ZZZzzzS so I am ready to roll when my connection comes in, or the like. It sucks sleeping in a chair because there are no hotel rooms left. Consider a micro sleeping pad. I got an awesome nap in Frankfurt laying in front of a big ass window in the sun during a 10 hour layover.
-Basic change of clothes
Civi set of clothes is nice, heavy duty set of pants like columbia cotton canvas or carhartts or the like with a lightweight shirt, smartwool socks, and travel/wicking underwear. Dont forget a watchcap, I like the smartwool or arcteryx ones.
-550 Cord and a couple of carabiners
A million and one uses. Last time I was in Central America my assistant locked the keys in the car with all of our gear in it. By shear luck I found a small piece of metal rod and use it and my dismantled 550 cord bracelet to pop the lock and get into the vehicle.
-Pen and paper
The ability to take notes and stay organized when plans change is paramount, shouldnt need to be said but it does.
-Basic med kit
Nothing big or bulky but some countries will sell you a viagra, testosterone, and antibiotics over the counter and some countries freak out if you ask for an aspirin. Bottom line, travel is hard on your system so keep some meds with you to keep you in tip top shape.
-Small flashlight
I keep a couple lights with me in my bag almost all the time but at least one good light is good. A handheld tac light is great for defense and finding that lost nicknack under the bed as you run out of your hotel room to catch your flight.
If I am on a short trip with no layover I minimize some of this stuff but if I have a multi-layover I will usually have most of this stuff because the chance of something going afoul is increased.
When I pick my tickets or get my itinerary from work I will immediately hit the net and find at least one or two good places to eat and a place to stay (for each layover) just in case.
Situational preparedness and forethought go a long way.