Hi Melissa,
The key to having both control and excitement is respect. If you present yourself as an organized and dedicated instructor that cares about students you will have both. The control comes with how you start and structure the class. This way the students know what is expected of them. The excitement comes with the activities, games, lectures, etc. that you prepare for your students. They know they will have a paced, organized class waiting for them that is informative, relevant, and engaging. By having this form of instructional preparation teaching then becomes much easier.
Gary
Hope this answers your question. If not let me know and I will expand on it further.