A CBP office checks a passenger's luggage and documents.

U.S. Customs and Border Protection

What Do I Need to Know Before I Travel Abroad?

Before you leave for vacation -- or even before you pack your bags -- you should know some of the laws that will affect you when you return to the U.S. from a foreign country. First of all, it's a good idea to take only the amount of personal medications that you'll need during your trip. In order to avoid customs problems, experts say you should leave each medication in its original container so that the drug name, dosage and physician's name are available for checking. Very large amounts of medications may raise "red flags" with customs officers. If you must carry these, take along a letter from your doctor and copies of your prescriptions.

Also, when you're packing, examine any electronics or expensive camera equipment you might be taking along. If that laptop was made in another country, you should register your ownership of it (complete with serial number or some other distinguishing mark) before you leave the U.S. (Customs provides special forms, Form 4457, for this purpose and you must show the item you're registering to an official). This certificate can be used on future trips. Without proof of ownership, you could be asked to pay duty on it again when you return home [source: U.S. Customs and Border Protection]. Other acceptable proofs of ownership include insurance documents, sales receipts and jewelry appraisals.

Mann, who is based in the Miami Customs office, emphasizes the importance of keeping your bags with you at all times when traveling and of refusing to accept bags or packages from strangers. There are reasons why airline agents ask if you've packed your own bags and kept them with you, and why airport announcements continually remind you that bags left unattended will be confiscated by airport security, he says. "Whether you're traveling outside the United States or inside, you don't want to carry or take someone else's bags or luggage or leave your own bags unattended. When you leave your bag unattended, this allows the opportunity for someone to put drugs inside it."

For a complete list of what you should know before you travel, check out the U.S. Customs and Border Protection Know Before You Go information. Another important bit of advice: If you observe suspicious activity or have information about smuggling or other fraudulent activities, call the Customs Service to report it at 1-800-Be-Alert. Information on reporting specific types of activity, including child kidnapping or exploitation, or illegal aliens, can by found on the U.S. Customs and Border Protection Web site.