To position the flag at half-staff, first raise the flag to the peak of the staff for an instant and then lower it to the half-staff position -- roughly halfway between the top and bottom of the staff.  Before lowering it for the day, raise the flag again to the peak of the pole for a moment.

By order of the President, the flag shall be flown at half-staff upon the death of principal figures of the United States Government and the Governor of a State, territory, or possession, as a mark of respect to their memory. In the event of the death of other officials or foreign dignitaries, the flag is to be displayed at half-staff according to U.S. Presidential instructions, or in accordance with recognized customs.

In the event of the death of a present or former official of the government of any State, territory, or possession of the U.S., the Governor of that State, territory, or possession may proclaim that the National Flag shall be flown at half-staff.

The flag shall be flown at half-staff for thirty days following the death of the President or a former President; ten days following the day of death of the Vice President, the Chief Justice or a retired Chief Justice of the United States, or the Speaker of the House of Representatives; from the day of death until interment of an Associate Justice of the Supreme Court, a Secretary of an executive or military department, a former Vice President or the Governor of a State, territory, or possession; and on the day of death and the following day for a Member of Congress.  The flag shall be flown at half-staff on Peace Officers Memorial Day, unless that day is also Armed Forces Day.

In a case where the flag is fixed to the pole (often in residential situations) it cannot be flown at half staff.   In this instance, it is proper to attach two black ribbons to the end of the pole (not the flag) to show respect.   (See mourning on the menu to the left.)