U.S. citizens:
Register with the Department of State’s Smart Traveler Enrollment Program (STEP). (https://step.state.gov/step/)

Canadian citizens:
Register with Registration of Canadians Abroad. (http://travel.gc.ca/travelling/registration)

U.K. citizens:
Register with Foreign and Commonwealth Office’s country-specific email alerts. (https://www.gov.uk/foreign-travel-advice)

Australian citizens:
Register with the Department of Foreign Affairs and Trade. (https://www.orao.dfat.gov.au/orao/weborao.nsf/Homeform?Openform)