The ex officio members of such commission shall meet forthwith at a time and place designated by the chairman of the board of county commissioners and proceed to select and appoint the eighteen (18) additional members and fix a date for an organizational meeting of such commission. On the date fixed for such meeting members of the commission shall select a chairman, vice-chairman and secretary, adopt rules of procedure, provide for regular meetings at least once each month, and designate such other officers and committees as may be deemed necessary. The members of the commission shall each be entitled to one vote and all acts of such commission shall be valid and effective when approved by a majority of the members of such commission. Vacancies in the citizen membership of the commission shall be filled by appointment of the remaining members of the commission.