Well, you might start with the
Network+ 007 Resources here in the CIN. You can review the Train-the-Trainer series, pick up handouts, and use that to form the basis for your class.
Have you decided on the text you're going to use? That's important because as Natuna said, you'll want to build up laboratory exercises. But regardless, getting several texts from different publishers can help build a pool of material that your students will find useful in learning, no matter what their learning style is.
Network+ is very term and concept heavy. You will want to know and explain definitions and acronyms, what they mean and more importantly, why they are there.
For example, DHCP - we know what it is, but why does it exist? What business problem does it solve? DHCP makes it much easier to configure IP addresses to nodes as well as populating fields like DNS, NTP, WINS, domain information, to keep one from having to touch every single client for IP configuration. By sharing this practical approach with students, concepts become less abstract, students begin to understand them better.
Looking at the course from the perspective of the student is really the best way to teach just about anything. Active learning, versus passive learning will help engage your students into the material. The more hands on you can do in the course, even with subnet calculations, the better off your course will be.
Good luck in there!
/r