All citizens looking to travel abroad are required to have a United States travel visa. That visa must not expire within six months of your plans to enter a foreign location. It's also advisable, but mandatory, to have a copy of your passport information for your protection.
This allows foreign customs to stamp your passport upon date of entry, effectively documenting how long you will be allowed to stay within their borders. Your passport will also identify you as a citizen to United States customs upon your return to the country.
You should also have your flight and hotel itinerary on hand as customs agents may request to know where you will be staying and when you will be leaving. Certain countries may be more or less strict with visitors, so it's best to be prepared at all times. In summary, you should have:
- Your Passport
- Flight & Hotel Itinerary
- Copies of the above in case of emergency