Try a chart, graph or illustration to clarify whatyou're talking about. Use pictures, graphs, charts, and color for variety andto draw the audience's eye to your most important points. Be sure the slideremains uncluttered . This gives youfreedom to move about and permits you to travel among and interact with youraudience. Keep the lights in the room as high as possible without washing out the imageon the screen.
Dark rooms lead to inattention, occasional sleeping, and theymake it impossible to take notes.
Besides, you can't be seen in the dark. Sometimes it is possible to remove the light bulbs or loosen tubes that shineon the projection screen. Consider print, overheads, 35mm slides, as well as computer slides. That way,no matter what happens to the equipment, or if the attendance is larger orsmaller than expected, you can adjust to the circumstances. Whenever possible, carry a backup disk of your presentation just in case yourcomputer crashes and you have to use a different machine.