The boy scout motto "be prepared" could also be a travel motto as bringing back-ups and doing research beforehand can be essential to a seamless experience.
Avoid the "oops"
It's simple, but often overlooked until the last moments - PACK ADAPTERS!
Why? They are needed for your electronics. Travel to other countries often requires adapter plugs that allow things like phones, computers and camera/battery chargers to fit the plug specifications for those countries.
We just returned from a trip to Ireland and Iceland. Ireland used three-pronged plugs. Icelandic configurations vary between two types of two-pin plugs. So, advance research on what you'll need in each place you plan to visit is important. Today, many modern hotel rooms in places like Europe have USB ports that will bypass the need for alternative plugs, but that's not a guarantee. Also, your camera or another electronic item may not have USB capability.
We need back-up, STAT!
Equally important is bringing a backup for both adapters and other vital items needed to keep your electronics running. Doing this becomes exponentially more important the farther you travel away from civilization. We have found that it's very easy to settle into a new hotel only to realize that you left your adapter plugged into the wall socket at the previous night's lodging. Similarly, various traveling companions have lost phone charging cords, camera battery chargers, and flashlights. And, sometimes, things just break. Large urban hotels often have a stash of all the electronic paraphernalia past guests have left behind, and they will allow you to borrow something during your stay. Or, when in Amsterdam or Rome, buying a replacement might not be a problem. However, in an Indian tiger reserve, miles from shopping, we're out of luck. So, we now routinely travel with backup for each critical item. Who wants to be on a wildlife photography safari with a camera that doesn't work because you can't charge the batteries?
One final note for photographers...
And, one final note, if you are doing a lot of photography, bring extra lenses! We usually travel with 35 mm cameras, so that means we each pack not only duplicate battery chargers, but also an extra lens cap filter, and plenty of photo storage cards. When Mike cracked a lens filter in the wilds of Alaska, the backup allowed him to snap on a new one right away.
Also available at Sunbury Press or wherever most books are sold.