After groups have been introduced to the topic, have some background information and understand the task, have them view the following assessment rubrics to guide their work.
Teacher Assessment Rubric - Multimedia Project
Student Self-Assessment Rubric - Group Work
After the conclusion of the WebQuest, have the student assess their own work in their group, as well as discuss your evaluation of their multimedia presentation.
Feel free to modify these rubrics to suit your own group and grade level.