(1) By personal service outside this state;
(2) By registered or certified mail to the last-known place of business, residence or abode within or outside this state of the person for whom the investigative demand is intended;
(3) In the manner provided for service of summons in an action or suit; or
(4) In accordance with the direction of a court. [1971 c.744 §15; 1975 c.437 §2; 2015 c.83 §3]