Upon arrival into another country, all passengers are required to go through immigration inspection. Immigration officials will ask you what the purpose of your visit is and how long you plan to stay in the country. You must have your passport, letter of invitation (if applicable), the appropriate visa stamp (if required), immunization records (if required) and proof of funding available for your time in the host country. They will inspect all of your documents and may or may not stamp your passport. It is very important that you remember to be polite and patient through this process. 

Once you have passed through immigration, you will go through customs. This is where you may be asked to declare certain items that you are bringing into the country. Be sure to declare any restricted items, since you may be subject to a search.   

Departure Tax
Several countries require a departure tax when you leave the country. It is important that you check to see if this will be required of you when you are ready to return and plan accordingly. In some countries, the departure tax must be paid in cash.

Returning to the U.S.
When you return from your trip abroad, there are things that you will have to consider. When re-entering the United States, you will have to pass through U.S. customs. You will want to have your receipts handy in case you need to support your purchases.

Currently, customs allows U.S. citizens to bring back $400.00 worth of merchandise that will remain duty free. The next $1000 worth of items are subject to a flat 10% rate. The United States allows a larger exemption from certain countries. It is wise for you to research the regulations on what you are allowed to bring back into the country upon your return in order to avoid any complications at customs.

Visit U.S. Customs for more information.