how to develop a new course as a new Assistant Professor I am writing to inquire some experiences/advices on developing a new course on my first semester (this fall) as an assistant professor in computer science. 

At this moment I am aware of the course assigned for me is for senior undergraduate students, principles of XXX (a subfield in computer science). According to previous years' feedback, this is roughly a 80 students course with 2 TA. 

I have been reaching out to the instructors who were teaching this course last year but unfortunately he refused to share his materials (is it common?). So before diving into the details and building the courses from scratch, I am writing to inquire some general experiences or lessons that could smooth the process a bit. So here are some questions and concerns:


What should I hash out before the new semester starts? This course is not "connected" to any other course, but maybe at least figure out something like typical expectations (and background) of the students? 
I took a similar course as a Ph.D. student but in my opinion that course simply goes too far. Perhaps it is a common (and wise) practice to start from there and develop my materials, say slides and projects? 
What is the common practice of reusing materials from other institutes? I often see some notes like "this slide is borrowed from XXX", but not sure about the best practice of doing (or avoid doing) so.
My major concern is about the time constraint, in my first semester. It would be great if I don't need to spend too much time at the very beginning and gradually refine the course after several semesters. So in that sense, what are some good strategies/tactics I can consider? For instance, considering to put more grades on the exam instead of homework? 


Any comments or suggestions would be appreciated very much. And I will be keeping an eye on this post for refinement, because clearly this current form is a bit too general. Thanks.
If you believe, as I do, that students learn from practice and feedback, not from seeing or hearing something once or twice, course design focuses on student tasks first. 

First decide what they will do to master the material of the course. Whether that is projects or exercises or exam prep (ugh) or whatever. Lay that out. All key concepts should have reinforcement activities (and feedback from you and the TAs). 

Knowing the student activities you can select learning materials that will be helpful to them in those activities - books, web sites, handouts, whatever. 

Now you have a pretty good idea what your lectures must cover. Note that not everything that you lecture on needs to be covered by exams and projects, but the core of it should be reinforced. If presentation of the core doesn't take up all the time, you can fill it in as you like.