A motion for continuance by either party shall be in writing unless made in a hearing in open court and shall be signed by the party or attorney requesting the continuance. The motion shall state all of the facts that the movant contends entitles the movant to a continuance. If a continuance is sought on the ground of non- availability of a witness, the motion must show when the witness will be available. The trial may be continued once upon the request of either party for not more than 120 days upon a showing of good cause, or by the court on its own motion in the interests of justice, when the person will not be substantially prejudiced. No additional continuances may be granted unless the court finds that a manifest injustice would otherwise occur. Continuances should only be ordered upon a showing of good cause. A motion for continuance on behalf of the respondent shall state that the respondent has been advised of all consequences of the request and of any rights waived by the motion.