Don’t overestimate your students’ research skills. Dissect the assignment and analyze skills needed to complete it. Consider working with a librarian to design instruction, tutorials, etc.
Don’t set limitations that are unclear or inappropriate to the assignment.
For example: Requiring scholarly journal articles for non-scholarly topics; Banning the use of “Internet” or “Online” resources. A large portion of our library’s resources is online and this terminology confuses students.