You can begin by identifying what your vision is for the blended course and how you can integrate it into your department's guidelines for blended courses. The course syllabus and outline must be clearly written to show the blended format and how each component of the course is delivered. Here it is also important to clearly describe to your students how interaction between you and them will take place within the course. For example, will you use your Course Management System's (CMS) e-mail or announcements tools to deliver information to your students? How should students contact you? How will assignments be delivered to students, and how should they submit them for grading? Will assessments take place in the classroom or online? Provide these instructions clearly, and stick with them throughout the course/semester. Set the expectations for interaction and explain why you have chosen the methods you will use.
Another consideration is to determine how you will build community within the course. Will there be group projects and assignments? Will groups meet in the classroom, or virtually via groups you create in the CMS course shell? Offer recommendations to students on how best to interact with their peers within their respective groups. Remember, a blended course format will be new to many students. Help them navigate this new learning territory by offering some "roadmaps" and best practices.
Finally, develop your strategy for how to handle technology support issues. They will come! Should students ask you for assistance in using the CMS and accessing your course? Should they contact the college's help desk? Again, set some guidelines so students feel comfortable knowing there is help available should they need it.
There are many more considerations to ponder when designing a blended course; these are just some broad categories that should be considered and planned for. Thoughtful redesign now will provide a better learning experience for your students later.