Create modules for each of the main “topics” within your course.  The advantage of this topic-based approach is you can easily adapt it for semesters that vary in length.  For example, you could have 15 topic-based modules and present one a week during fall and spring semesters, and then if you transition to a 7-week summer semester you could release 2 topic-based content modules a week to your students.

Create modules for learning outcomes within your course.  The advantage of this learning outcomes-based approach is you can easily adapt it for semesters that vary in length.  For example, you could have 15 learning outcome-based modules and present one a week during fall and spring semesters, then if you transition to a 7-week summer semester you could release 2 learning outcome-based content modules a week to your students.

Create modules that include all the content, activities, and assessments you want your students to do each week.  This method works well for helping students stay on track and manage their time.  It also complies with the recommendation to have modules become available on a specific date and time each week.  For example, all modules can open at 8:00 am on Monday and all activities/assessments can be due on Sundays at 11:59 pm.
This organizational method can involve more work for the instructor when switching from a 16-week semester to a 7-week semester.

If you have decided on an assessment strategy that includes 4 exams (or other forms of assessment) you can create 4 modules for your course and all of the content, and activities for the first assessment are included in the unit 1 module, etc.