Leave all expensive and unneeded personal or professional property at home. Check with your medical insurance carrier about coverage away from your home and work. Avoid a demanding schedule upon your arrival if you have traveled across many time zones. Give yourself a chance to adjust to new surroundings. Consider leaving them at home.
Most foreign airports are very serious about security.
Be prepared to be questioned and always answer customs' questions honestly. Do not exchange much currency before you enter your destination country. Exchange rates in hotels are typically not very good. Check your destination country's holidays. Usually public transportation, gas stations, and grocery stores are not open on holidays.