Where do I start?
Choose the module you want to work on. When you've done that, look at the learning objectives, activities, and assignments you've decided on for that module. These should be listed very clearly on your course plan already. Isolate your activities and assessments so you can see only those and nothing else is distracting you. Maybe you need to paste them on a completely separate document where you have room to brainstorm.
Look at the assessment(s) you want to provide for your students for the module you've chosen. Does it accurately measure the learning objectives you have for the module? Now, look at your course activities. Do they accomplish everything the student would need to do to prepare for the assessment you would like to provide for the students? If any modifications need to be made, now is a good time.
The module development process is not necessarily linear; that is, you don't need to be strict about creating your assessment completely and then moving on to your activities. Think of it more as a fluid, nebulous process where you do what is easiest first! If you already know what your activities need to look like, but you haven't decided on each individual quiz question, that's okay! Design your activities first, and write the quiz questions later. On the other hand, if you already know that the students will be creating a multimedia presentation on a topic to be presented to their classmates as their assessment, and you know what that presentation should look like, go ahead and create the instructions for it, a rubric for grading, and perhaps an example. This will tell you what your activities to prepare the students to create that presentation should look like.
To sum up, in this unit, we are filling in that gap between your [learning objectives, activities, and assessments] and [what the student actually does in the class] for one module. We'll look at a couple of examples below, just in case you want to see how I've done it in the past.