Batteries
The number one mistake I see most often made by people traveling with cameras is not having enough fresh batteries.
Depending on your camera and flash, you may need more than just one extra battery. For example, my Nikon D4 camera can go most of a day shooting still images with one battery; however, if I start to shoot video or spend a lot of time reviewing images on my LCD, I can drain the battery and need a second.
My Fuji X-E2 goes through batteries, and I used all three batteries the day before.
I recommend having at least one extra battery, and before you leave for the day of shooting, be sure to charge both batteries fully.
Every evening before you turn in for bed, be sure to recharge all your batteries. That way, they will all be ready for another full day of shooting your travel in the morning.
Memory Cards
Carrying a few extra memory cards on a trip is much easier than a laptop computer.
For a once in a lifetime trip, it is wise to keep all the images on cards until you have them all on your computer and backed up in another location before formatting your cards.
Memory Card Tip
Always format your cards in your camera and not on your computer. The camera will do a better job of clearing the cards and creating the proper directories needed for the card to work correctly with the camera.