Maryland Code, Public Safety § 13-703

(1) stating the substance of the order or reading the order to the individual warned;

(2) leaving a copy of the order at the last known place of residence or business of the individual;

(3) mailing a copy of the order to the last known residence or business address of the individual; or

(4) sending the substance of the order via electronic communication, including telephone, cellular phone, facsimile, or electronic mail.

(b)(1) If required by the officer issuing the order, the officer or noncommissioned officer giving warning shall make a return of warning containing the name of the individual warned and the time, place, and manner of warning.

(2) A return of warning: