The number one mistake I see most often made by people traveling with their camera is not having enough fresh batteries.
Depending on your camera and flash you may need more than just one extra battery. 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 then I can drain the battery and need a second.
My Fuji X-E2 goes through batteries and I have used all three batteries in a day before.
I recommend having at least one extra battery and before you leave for the day of shooting be sure both batteries are fully charged.
Every evening before you turn in for bed, be sure to recharge all your batteries. That way in the morning they will all be ready for another full day of shooting your travel.
It is much easier to carry a few extra memory cards on a trip than it is to carry a laptop computer.
When this is 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 as well 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 not just clearing the cards but creating the proper directories needed for the card to work properly with the camera.