Register with the State Department using online service at https://travelregistration.state.gov to help contact when travelling in the US. This is important if family members back home need to get in touch for some urgent reason.
Familiarize with local laws and conditions as these are extremely important. What may not be `wrong’ in one country could very well be a criminal offence in another. To avoid trouble, it is better to be up to date with all laws and conditions which directly impact you.
In case of emergencies contact: 1-888-407-4747, if calling from the U.S. or Canada, or 202-501-4444, if calling from overseas.