Predetermined outlines tend to work best, especially if they contain clearly defined headings. Overhead projectors can display a great deal more than just writing. Graphs and cartoons are a possibility, as are silhouettes and small, opaque objects. Enlarged newspaper articles and other print materials can be copied by putting the blank transparency in a photocopier. It is also possible, through a special liquid crystal display panel, to directly project a normal computer display onto the large screen.
Cartoons are an excellent way of simplifying complex ideas and adding humor.
With a little effort, spatial, statistical, and structural relationships can all be visualized on an overhead. The projector is best turned off when the instructor is not directly referring to the overhead. Many instructors use a piece of blank paper to cover part of the transparency so that only the point being developed is revealed. It is also important never to leave a transparency on the screen so long that it becomes boring. Video lends itself to classroom use extremely well.