Make sure you have a signed, valid passport, and a visa, if required, and fill in the emergency information page of your passport.
Leave copies of your itinerary, passport data page and visas with family or friends, so you can be contacted in case of an emergency.
Ask your medical insurance company if your policy applies overseas, and if it covers emergency expenses such as medical evacuation. If it does not, consider supplemental insurance.
To avoid being a target of crime, do not wear conspicuous clothing or jewelry and do not carry excessive amounts of money. Also, do not leave unattended luggage in public areas and do not accept packages from strangers.