What resources do you use when developing a new course from scratch?
I'd go back and consult one of those "How to teach" books you've probably got lying around and focus on doing a good job of stating the course's Learning Objectives. Then, I'd make sure that the course material, the learning activities and assessment tasks are properly aligned with those objectives. 

I would then make sure the students get to see those objectives and to understand how what they will be doing fits with those objectives. 

I would design some sample assessment activities, such as sample exam questions (if that is one of your planned means of assessment). Then I would make sure that the content of your course is sufficient to enable students to do such assignments or answer such questions. 

Mckeachie's Teaching Tips is an excellent resource for helping you do this. And it never hurts to refresh your didactic skills.