For detailed information about steps you can take to ensure a safe trip, see How to Have a Safe Trip.  Meanwhile, here are some quick tips to make your travel easier and safer:  

Register so the State Department can better assist you in an emergency:  Register your travel plans  with the State Department through a free online service at https://travelregistration.state.gov.  This will help us contact you if there is a family emergency in the U.S., or if there is a crisis where you are traveling.  In accordance with the Privacy Act, information on your welfare and whereabouts will not be released to others without your express authorization.

Sign passport, and fill in the emergency information:  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 itinerary and passport data page:  Leave copies of your itinerary, passport data page and visas with family or friends, so you can be contacted in case of an emergency.

Check your overseas medical insurance coverage:  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.

Familiarize yourself with local conditions and laws:   While in a foreign country, you are subject to its laws.  The State Department web site at http://travel.state.gov/travel/cis_pa_tw/cis/cis_1765.html has useful safety and other information about the countries you will visit. 

Take precautions to avoid being a target of crime:  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.

Contact us in an emergency: Consular personnel at U.S. Embassies and Consulates abroad and in the U.S. are available 24 hours a day, 7 days a week, to provide emergency assistance to U.S. citizens.  Contact information for U.S. Embassies and Consulates appears on the Bureau of Consular Affairs website at http://travel.state.gov.  Also note that the Office of Overseas Citizen Services in the State Department’s Bureau of Consular Affairs may be reached for assistance with emergencies at 1-888-407-4747, if calling from the U.S. or Canada, or 202-501-4444, if calling from overseas. 

Source from here

* When you have the plan to trip in Manhattan, What about New York walking tours