All assignments, from ungraded formative response papers all the way up to a capstone assignment, should include the following components to ensure that students and teachers understand not only the learning objective of the assignment, but also the discrete steps which they will need to follow in order to complete it successfully.
Preamble. This situates the assignment within the context of the course, reminding students of what they have been working on in anticipation of the assignment and how that work has prepared them to succeed at it.
Justification and Purpose. This explains why the particular type or genre of assignment you’ve chosen (e.g., lab report, policy memo, problem set, or personal reflection) is the best way for you and your students to measure how well they’ve met the learning objectives associated with this segment of the course.
Mission. This explains the assignment in broad brush strokes, giving students a general sense of the project, you are setting before them. It often gives students guidance on the evidence or data they should be working with, as well as helping them imagine the audience their work should be aimed at.
Tasks. This outlines what students are supposed to do at a more granular level: for example, how to start, where to look, how to ask for help, etc. If written well, this part of the assignment prompt ought to function as a kind of "process" rubric for students, helping them to decide for themselves whether they are completing the assignment successfully.
Submission format. This tells students, in appropriate detail, which stylistic conventions they should observe and how to submit their work. For example, should the assignment be a five-page paper written in APA format and saved as a .docx file? Should it be uploaded to the course website? Is it due by Tuesday at 5:00pm?