Watch your Cash!
Don’t bring more than two credit cards with you on a vacation. Furthermore, make sure those companies know you are traveling. If you don’t inform them, they may freeze your card for suspicious overseas activity. If you have a hotel safe, use it. If not, be sure to only bring what you need with you when you go out. If you want to get really hardcore, purchase a money belt or neck wallet in order to keep your passport and extra cash in a safe place close to your body. Now if that is too extreme for you, just be aware of suspicious people and keep your wallet in the front of your pants. You already look out of place, so having a wallet in the front of your pants won’t make that much of a style difference.
Passports (don’t wait until the last minute to see if they are expired!)
Insurance Cards (also check with your insurance agency for short term travel coverage)
Make sure your luggage has tags with your name and contact information on them.
Rain protection; bring a mini Umbrella or a light Raincoat.
Toiletries: cosmetics, deodorant, shampoo, shaving needs etc.
Phone Charger (this may include having to buy a Voltage Converter overseas)
Floss, Toothbrush, Nail Clippers
Swimsuit, Sun block
Some extra batteries for things such as Cameras and Alarm Clocks
Be aware of any medical conditions you have, bring Aspirin in the U.S. before you leave so you’re sure and comfortable with any medications you are ingesting. Bug repellent for exotic vacations, and if you have problem flying, look into purchasing some Airborne.