A combination of the three is generally considered best, as varied information keeps classes lively. Spoken word and dialog are represented by lectures and discussion groups. But visual aids have been largely neglected, thrown a bone by the occasional transparency or blackboard notation, and less often by slides or movies. Modern technology allows great variation in the visuals accompanying lectures. A document reader can project any document or small object onto a screen, without requiring slides to be made.
Lecturers can program DVDs to show timed sections of recorded materials in any order.
And data projectors allow any computer file or Web page to play a role in class. Designing a truly effective classroom isn't just a matter of introducing items into an already existing space. Ideally, the classroom will be designed around the technology, taking into account the arrangements of seats, the placement of items, and the location of the lectern. The professor shouldn't have to check what's on a screen over his or her shoulder, shouldn't be blocking visual aids, and probably wants a clear path in which to pace. Even lighting has to balance the needs of note-taking against having clear images on the screen.