Most students have an optimal attention span of about 12 minutes, therefore instructors should talk for no longer than 15 minutes before taking a mini break of at least 2 minutes. Include various modes of teaching, for example, visual aids, guest speaker, short video clips or periods of reflective silence to enhance a lecture. Other essential components to a stimulating lecture include, speaking from untypical areas in the classroom, using clear body language and signals to indicate an important point or moving on, using questions to stimulate thought at the beginning and close of the lecture and presenting alternate perspectives of view on the topic.
Most importantly an instructor should regularly review his lecturing thru student evaluation questionnaires like the CIQ, peer reviews or video taping yourself. This will help the instructor to become aware of habits and behaviors that may need modifying or eliminating in order to improve presentations skills.
Brookfield, S., (2006). The Skillful Teacher:
On Technique, Trust, and Responsiveness in the Classroom {Jossey-bass Higher
and Adult Education Series; 2nd Ed.}. John Wiley
& Sons, (US).