Circle or underline specific items on the transparency. Make sure you use water-soluble overhead transparency pens. Expose information as needed. Number your transparencies sequentially as they are to be used. If you need to use the same visual twice, make a second transparency of it.
Slides Make sure the room is appropriately set up for viewing slides.
Number each slide in case they are dropped. Stand facing an audience and use a remote control to advance the slides. When using slides and overhead transparencies simultaneously, darken your transparency with a color overlay sheet. Leave an empty slot after every few slides. The projector will shut off automatically when a blank slot is left between slides, allowing for discussion.