Previously prepared sheets of acetate are best and especially if a type written sheet is photocopied.
Use of colour, diagrams and simple key words are most important, with the material being uncovered as the presentation progresses.
If handouts contain the same or similar material as the talk, it is helpful to say so, enabling the audience to concentrate on the visual display.
The O.H.P. Display should be readily seen by the whole audience, who might be asked about this point at the being of its use.
Care with trailing leads should be taken and people warned if necessary.
If a discussion makes use of an O.H.P., again key words and phrases can be noted on the screen, but this time directly.
A major advantage of the O.H.P. is that the operator can have a full view of his or her audience at all times.