One best practice that that has been implemented to meet the Public Information and Warning capability is National Terrorism Advisory System (NTAS) Advisories. Information on credible terrorist threats is provided to the public primarily through these advisories. Under NTAS, DHS will coordinate with other Federal entities in order to issue detailed advisories to the public when the Federal Government receives information about a credible terrorist threat. NTAS Advisories provide the DHS Secretary with a scalable and agile means of disseminating information regarding threats or risks of terrorism to the homeland to Federal, state, local, tribal, and territorial government authorities, and to the people of the United States, as appropriate.
NTAS sample advisories can be found at: https://www.dhs.gov /publication/national-terrorism-advisory-system-sample-advisories
The NTAS advisories help meet the Public Information and Warning critical task of increasing public awareness of indicators of terrorism and terrorism-related crime. These advisories also help meet the critical task of sharing prompt and actionable messages, to include NTAS alerts, with the public and other stakeholders, as appropriate, to aid in the prevention of imminent follow-on terrorist attacks.