Purchase a money belt or pouch for cash, plane tickets, and passport. Wear this inside your clothing when traveling. Don't take the family jewelry or items that have great sentimental value. Leave them at home where you will be sure they will not be lost or stolen. In fact, you shouldn't pack anything you can't afford to lose.
Luggage can occasionally go astray.
Don't pack valuables in checked suitcases. Clean out your wallet before you leave. You probably don't need your Wild Shopper cards while studying abroad. Leave these and all unneeded papers at home. Register imported items, such as tape recorders, cameras, watches, etc. with U.S. Customs before leaving the States.