Students respond well to things they perceive as relevant. Doing presentations well requires many skills, such as how to plan ahead, work in a group, how to gather and assess information, etc. These must be taught separately from, and prior to the beginning of, the presentation unit because it is too difficult to learn both new content and new skills simultaneously. Once the required skills become second nature, the students will be competent enough to apply them to scientific content. Once this has been done, let the students discuss what was good and bad about these presentations, and develop requirements and a scoring rubric for the next set, the real ones.
Students tend to adhere more closely to requirements they generate themselves.
Serious quantities of time are devoted to developing a calendar, content requirements, gathering of resource materials, copying and teaching formats. It helps a lot to collaborate with another teacher to divide up the work load. Student prep time is designated by the calendar given to them by the teacher. I never get through a series in less than 4-6 weeks minimum. Cooperative groups of students collect information, digest and rephrase it in a suitable manner for their peers and disseminate it via presentation.