Register your trip with the U.S. Department of State's Smart Traveler Enrollment Program (STEP)

If you are a U.S. citizen, register your trip with the U.S. Department of State’s Smart Traveler Enrollment Program (STEP) so they can better assist you in an emergency, i.e. you lose your passport. You can also subscribe to receive country specific updates. If you are not a U.S. citizen, the Department of State's equivalent in your country might have a similar program. 

Timeframe: 
A few weeks before your trip

Link: 
U.S. Department of State Smart Traveler Enrollment Program