Final answer:
The method of letting clients know ahead of time the nature, expectations, and goals of the group, especially in mandatory groups is Group Contract.
Step-by-step explanation:
The method of letting clients know ahead of time the nature, expectations, and goals of the group, especially in mandatory groups is Group Contract. A group contract is a set of group expectations for appropriate thoughts and behaviors of its members. It outlines the rules, responsibilities, and goals of the group, which helps establish a clear understanding among the participants.