10 Things you MUST pack
Dehydration kit: Sitting on an airplane can dry you out but don’t panic, dehydration kits need not be elaborate. All you really need is an empty water bottle (many airports have refill stations), and a cap for sunny days and you’re good to go.
Charging cords: Phones and tablets die. They’ll stay dead too if you forget your charger cords. Pack them (and maybe a back-up) and don’t forget the portable charger.
Cash & cards: Yes, this is a no brainer, but last-minute trip snags plus frenzied packing has caused more than one traveller to lose his mind. Tip: If you’ll be heading to another country, go to the bank ahead of time and get the local currency; it could come in handy.
Documents and photos: Remember how phones and tablets die? It happens at inconvenient moments so even if your boarding pass is on your phone, print it out. If traveling internationally, photocopy your passport, too. Add a couple of extra passport photos, too; you’ll need them if you have to go to an embassy or consulate for an emergency replacement.
Indestructible snacks like a couple of granola or power bars in your carry-on.
Entertainment: Put books and movies on an electronic device. Add your own favorite airplane/airport time-killer.
The right clothes: Don’t pack anything you’re not crazy about because you won’t wear it and it’ll just take up space. Plus, if those shorts are brand new, you don’t really know if they’re comfortable. As for shoes, they absolutely must be comfortable (vacations are not for breaking in hiking boots, either). Add one of those freebie sewing kits (in case anything happens to the outfit you do like)
Bathing suit: There may be a pool in the hotel or a lake excursion no one’s mentioned. A suit takes up almost zero room and weighs next to nothing.
Eye wear: Don’t forget your sunglasses. And if you wear regular glasses or contacts, pack a second pair.
Health essentials: Pack your vitamins, daily medications, maybe some aspirin and upset stomach remedies plus a few Band-Aids. Complete the mini-first aid kit with hand sanitizer wipes. Then use them first thing to wipe off your seatback tray table (people have been known to put their feet on those things).